diff --git a/.github/workflows/run_tests.yml b/.github/workflows/run_tests.yml
index 008aa639e..eaa0b80df 100644
--- a/.github/workflows/run_tests.yml
+++ b/.github/workflows/run_tests.yml
@@ -71,10 +71,10 @@ jobs:
         run: go test -v ./... -coverprofile=./coverage.txt -covermode=atomic -coverpkg=./pkg...,./cli/...
 
       - name: Upload coverage results to Codecov
-        uses: codecov/codecov-action@v1
+        uses: codecov/codecov-action@v2
         with:
-          fail_ci_if_error: false
-          path_to_write_report: ./coverage.txt
+          fail_ci_if_error: true # if something is wrong on uploading codecov results, then this job will fail
+          files: ./coverage.txt
           verbose: true
 
   tests:
diff --git a/cli/contract_test.go b/cli/contract_test.go
index c94dc1ba3..7ecacd70d 100644
--- a/cli/contract_test.go
+++ b/cli/contract_test.go
@@ -56,15 +56,24 @@ func TestCalcHash(t *testing.T) {
 	t.Run("no manifest file", func(t *testing.T) {
 		e.RunWithError(t, append(cmd, "--sender", sender.StringLE(), "--in", nefPath)...)
 	})
-	t.Run("invalid path", func(t *testing.T) {
+	t.Run("invalid nef path", func(t *testing.T) {
 		e.RunWithError(t, append(cmd, "--sender", sender.StringLE(),
 			"--in", "./testdata/verify.nef123", "--manifest", manifestPath)...)
 	})
-	t.Run("invalid file", func(t *testing.T) {
+	t.Run("invalid manifest path", func(t *testing.T) {
+		e.RunWithError(t, append(cmd, "--sender", sender.StringLE(),
+			"--in", nefPath, "--manifest", "./testdata/verify.manifest123")...)
+	})
+	t.Run("invalid nef file", func(t *testing.T) {
 		p := filepath.Join(tmpDir, "neogo.calchash.verify.nef")
 		require.NoError(t, ioutil.WriteFile(p, src[:4], os.ModePerm))
 		e.RunWithError(t, append(cmd, "--sender", sender.StringLE(), "--in", p, "--manifest", manifestPath)...)
 	})
+	t.Run("invalid manifest file", func(t *testing.T) {
+		p := filepath.Join(tmpDir, "neogo.calchash.verify.manifest.json")
+		require.NoError(t, ioutil.WriteFile(p, manifestBytes[:4], os.ModePerm))
+		e.RunWithError(t, append(cmd, "--sender", sender.StringLE(), "--in", nefPath, "--manifest", p)...)
+	})
 
 	cmd = append(cmd, "--in", nefPath, "--manifest", manifestPath)
 	expected := state.CreateContractHash(sender, nefF.Checksum, manif.Name)
@@ -123,6 +132,13 @@ func TestContractInitAndCompile(t *testing.T) {
 		cfgName := filepath.Join(ctrPath, "notexists.yml")
 		e.RunWithError(t, append(cmd, "--config", cfgName)...)
 	})
+	t.Run("provided corrupted config", func(t *testing.T) {
+		data, err := ioutil.ReadFile(cfgPath)
+		require.NoError(t, err)
+		badCfg := filepath.Join(tmpDir, "bad.yml")
+		require.NoError(t, ioutil.WriteFile(badCfg, data[:len(data)-5], os.ModePerm))
+		e.RunWithError(t, append(cmd, "--config", badCfg)...)
+	})
 
 	// Replace `pkg/interop` in go.mod to avoid getting an actual module version.
 	goMod := filepath.Join(ctrPath, "go.mod")
@@ -263,6 +279,45 @@ func TestDeployWithSigners(t *testing.T) {
 		"--config", "testdata/deploy/neo-go.yml",
 		"--out", nefName, "--manifest", manifestName)
 
+	t.Run("missing nef", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", validatorWallet, "--address", validatorAddr,
+			"--in", "", "--manifest", manifestName)
+	})
+	t.Run("missing manifest", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", validatorWallet, "--address", validatorAddr,
+			"--in", nefName, "--manifest", "")
+	})
+	t.Run("corrupted data", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", validatorWallet, "--address", validatorAddr,
+			"--in", nefName, "--manifest", manifestName,
+			"[", "str1")
+	})
+	t.Run("invalid data", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", validatorWallet, "--address", validatorAddr,
+			"--in", nefName, "--manifest", manifestName,
+			"str1", "str2")
+	})
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--address", validatorAddr,
+			"--in", nefName, "--manifest", manifestName,
+			"[", "str1", "str2", "]")
+	})
+	t.Run("missing RPC", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "deploy",
+			"--wallet", validatorWallet, "--address", validatorAddr,
+			"--in", nefName, "--manifest", manifestName,
+			"[", "str1", "str2", "]")
+	})
 	e.In.WriteString("one\r")
 	e.Run(t, "neo-go", "contract", "deploy",
 		"--rpc-endpoint", "http://"+e.RPC.Addr,
@@ -292,6 +347,54 @@ func TestContractManifestGroups(t *testing.T) {
 		"--config", "testdata/deploy/neo-go.yml",
 		"--out", nefName, "--manifest", manifestName)
 
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group")
+	})
+	t.Run("invalid wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", t.TempDir())
+	})
+	t.Run("invalid account", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", "not-an-acc")
+	})
+	t.Run("invalid sender", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", testWalletAccount,
+			"--sender", "not-a-sender")
+	})
+	t.Run("invalid NEF file", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", testWalletAccount,
+			"--sender", testWalletAccount, "--nef", tmpDir)
+	})
+	t.Run("corrupted NEF file", func(t *testing.T) {
+		f := filepath.Join(tmpDir, "invalid.nef")
+		require.NoError(t, ioutil.WriteFile(f, []byte{1, 2, 3}, os.ModePerm))
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", testWalletAccount,
+			"--sender", testWalletAccount, "--nef", f)
+	})
+	t.Run("invalid manifest file", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", testWalletAccount,
+			"--sender", testWalletAccount, "--nef", nefName,
+			"--manifest", tmpDir)
+	})
+	t.Run("corrupted manifest file", func(t *testing.T) {
+		f := filepath.Join(tmpDir, "invalid.manifest.json")
+		require.NoError(t, ioutil.WriteFile(f, []byte{1, 2, 3}, os.ModePerm))
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", testWalletAccount,
+			"--sender", testWalletAccount, "--nef", nefName,
+			"--manifest", f)
+	})
+	t.Run("unknown account", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "manifest", "add-group",
+			"--wallet", testWalletPath, "--account", util.Uint160{}.StringLE(),
+			"--sender", testWalletAccount, "--nef", nefName,
+			"--manifest", manifestName)
+	})
 	cmd := []string{"neo-go", "contract", "manifest", "add-group",
 		"--nef", nefName, "--manifest", manifestName}
 
@@ -338,6 +441,44 @@ func deployContract(t *testing.T, e *executor, inPath, configPath, wallet, addre
 	return h
 }
 
+func TestContract_TestInvokeScript(t *testing.T) {
+	e := newExecutor(t, true)
+	tmpDir := t.TempDir()
+	badNef := filepath.Join(tmpDir, "invalid.nef")
+	goodNef := filepath.Join(tmpDir, "deploy.nef")
+	manifestName := filepath.Join(tmpDir, "deploy.manifest.json")
+	e.Run(t, "neo-go", "contract", "compile",
+		"--in", "testdata/deploy/main.go", // compile single file
+		"--config", "testdata/deploy/neo-go.yml",
+		"--out", goodNef, "--manifest", manifestName)
+
+	t.Run("missing in", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "testinvokescript",
+			"--rpc-endpoint", "http://"+e.RPC.Addr)
+	})
+	t.Run("unexisting in", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "testinvokescript",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--in", badNef)
+	})
+	t.Run("invalid nef", func(t *testing.T) {
+		require.NoError(t, ioutil.WriteFile(badNef, []byte("qwer"), os.ModePerm))
+		e.RunWithError(t, "neo-go", "contract", "testinvokescript",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--in", badNef)
+	})
+	t.Run("invalid signers", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "testinvokescript",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--in", goodNef, "--", "not-a-valid-signer")
+	})
+	t.Run("no RPC endpoint", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "contract", "testinvokescript",
+			"--rpc-endpoint", "http://123456789",
+			"--in", goodNef)
+	})
+}
+
 func TestComlileAndInvokeFunction(t *testing.T) {
 	e := newExecutor(t, true)
 
@@ -436,6 +577,33 @@ func TestComlileAndInvokeFunction(t *testing.T) {
 				h.StringLE(), "getValue")
 			e.RunWithError(t, cmd...)
 		})
+		t.Run("corrupted wallet", func(t *testing.T) {
+			tmp, err := ioutil.TempDir("", "tmp")
+			require.NoError(t, err)
+			tmpPath := filepath.Join(tmp, "wallet.json")
+			require.NoError(t, ioutil.WriteFile(tmpPath, []byte("{"), os.ModePerm))
+
+			cmd := append(cmd, "--wallet", tmpPath,
+				h.StringLE(), "getValue")
+			e.RunWithError(t, cmd...)
+		})
+		t.Run("non-existent address", func(t *testing.T) {
+			cmd := append(cmd, "--wallet", validatorWallet,
+				"--address", random.Uint160().StringLE(),
+				h.StringLE(), "getValue")
+			e.RunWithError(t, cmd...)
+		})
+		t.Run("invalid password", func(t *testing.T) {
+			e.In.WriteString("invalid_password\r")
+			cmd := append(cmd, "--wallet", validatorWallet,
+				h.StringLE(), "getValue")
+			e.RunWithError(t, cmd...)
+		})
+		t.Run("good: default address", func(t *testing.T) {
+			e.In.WriteString("one\r")
+			e.In.WriteString("y\r")
+			e.Run(t, append(cmd, "--wallet", validatorWallet, h.StringLE(), "getValue")...)
+		})
 
 		cmd = append(cmd, "--wallet", validatorWallet, "--address", validatorAddr)
 		t.Run("cancelled", func(t *testing.T) {
diff --git a/cli/dump_test.go b/cli/dump_test.go
index ae2719fff..1d42283eb 100644
--- a/cli/dump_test.go
+++ b/cli/dump_test.go
@@ -4,6 +4,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strconv"
 	"testing"
 
 	"github.com/nspcc-dev/neo-go/pkg/config"
@@ -11,15 +12,19 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
-func TestDBRestore(t *testing.T) {
+func TestDBRestoreDump(t *testing.T) {
 	tmpDir := t.TempDir()
 
-	chainPath := filepath.Join(tmpDir, "neogotestchain")
-	cfg, err := config.LoadFile(filepath.Join("..", "config", "protocol.unit_testnet.yml"))
-	require.NoError(t, err, "could not load config")
-	cfg.ApplicationConfiguration.DBConfiguration.Type = "leveldb"
-	cfg.ApplicationConfiguration.DBConfiguration.LevelDBOptions.DataDirectoryPath = chainPath
+	loadConfig := func(t *testing.T) config.Config {
+		chainPath := filepath.Join(tmpDir, "neogotestchain")
+		cfg, err := config.LoadFile(filepath.Join("..", "config", "protocol.unit_testnet.yml"))
+		require.NoError(t, err, "could not load config")
+		cfg.ApplicationConfiguration.DBConfiguration.Type = "leveldb"
+		cfg.ApplicationConfiguration.DBConfiguration.LevelDBOptions.DataDirectoryPath = chainPath
+		return cfg
+	}
 
+	cfg := loadConfig(t)
 	out, err := yaml.Marshal(cfg)
 	require.NoError(t, err)
 
@@ -29,6 +34,7 @@ func TestDBRestore(t *testing.T) {
 	// generated via `go run ./scripts/gendump/main.go --out ./cli/testdata/chain50x2.acc --blocks 50 --txs 2`
 	const inDump = "./testdata/chain50x2.acc"
 	e := newExecutor(t, false)
+
 	stateDump := filepath.Join(tmpDir, "neogo.teststate")
 	baseArgs := []string{"neo-go", "db", "restore", "--unittest",
 		"--config-path", tmpDir, "--in", inDump, "--dump", stateDump}
@@ -47,8 +53,50 @@ func TestDBRestore(t *testing.T) {
 
 	// Dump and compare.
 	dumpPath := filepath.Join(tmpDir, "testdump.acc")
-	e.Run(t, "neo-go", "db", "dump", "--unittest",
-		"--config-path", tmpDir, "--out", dumpPath)
+
+	t.Run("missing config", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "db", "dump", "--privnet",
+			"--config-path", tmpDir, "--out", dumpPath)
+	})
+	t.Run("bad logger config", func(t *testing.T) {
+		badConfigDir := t.TempDir()
+		logfile := filepath.Join(badConfigDir, "logdir")
+		require.NoError(t, ioutil.WriteFile(logfile, []byte{1, 2, 3}, os.ModePerm))
+		cfg = loadConfig(t)
+		cfg.ApplicationConfiguration.LogPath = filepath.Join(logfile, "file.log")
+		out, err = yaml.Marshal(cfg)
+		require.NoError(t, err)
+
+		cfgPath = filepath.Join(badConfigDir, "protocol.unit_testnet.yml")
+		require.NoError(t, ioutil.WriteFile(cfgPath, out, os.ModePerm))
+
+		e.RunWithError(t, "neo-go", "db", "dump", "--unittest",
+			"--config-path", badConfigDir, "--out", dumpPath)
+	})
+	t.Run("bad storage config", func(t *testing.T) {
+		badConfigDir := t.TempDir()
+		logfile := filepath.Join(badConfigDir, "logdir")
+		require.NoError(t, ioutil.WriteFile(logfile, []byte{1, 2, 3}, os.ModePerm))
+		cfg = loadConfig(t)
+		cfg.ApplicationConfiguration.DBConfiguration.Type = ""
+		out, err = yaml.Marshal(cfg)
+		require.NoError(t, err)
+
+		cfgPath = filepath.Join(badConfigDir, "protocol.unit_testnet.yml")
+		require.NoError(t, ioutil.WriteFile(cfgPath, out, os.ModePerm))
+
+		e.RunWithError(t, "neo-go", "db", "dump", "--unittest",
+			"--config-path", badConfigDir, "--out", dumpPath)
+	})
+
+	baseCmd := []string{"neo-go", "db", "dump", "--unittest",
+		"--config-path", tmpDir, "--out", dumpPath}
+
+	t.Run("invalid start/count", func(t *testing.T) {
+		e.RunWithError(t, append(baseCmd, "--start", "5", "--count", strconv.Itoa(50-5+1+1))...)
+	})
+
+	e.Run(t, baseCmd...)
 
 	d1, err := ioutil.ReadFile(inDump)
 	require.NoError(t, err)
diff --git a/cli/executor_test.go b/cli/executor_test.go
index 5ff7b2996..a82d8fc32 100644
--- a/cli/executor_test.go
+++ b/cli/executor_test.go
@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"math"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -58,13 +59,66 @@ type executor struct {
 	// NetSrv is a network server (can be empty).
 	NetSrv *network.Server
 	// Out contains command output.
-	Out *bytes.Buffer
+	Out *ConcurrentBuffer
 	// Err contains command errors.
 	Err *bytes.Buffer
 	// In contains command input.
 	In *bytes.Buffer
 }
 
+// ConcurrentBuffer is a wrapper over Buffer with mutex.
+type ConcurrentBuffer struct {
+	lock sync.RWMutex
+	buf  *bytes.Buffer
+}
+
+// NewConcurrentBuffer returns new ConcurrentBuffer with underlying buffer initialized.
+func NewConcurrentBuffer() *ConcurrentBuffer {
+	return &ConcurrentBuffer{
+		buf: bytes.NewBuffer(nil),
+	}
+}
+
+// Write is a concurrent wrapper over the corresponding method of bytes.Buffer.
+func (w *ConcurrentBuffer) Write(p []byte) (int, error) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	return w.buf.Write(p)
+}
+
+// ReadString is a concurrent wrapper over the corresponding method of bytes.Buffer.
+func (w *ConcurrentBuffer) ReadString(delim byte) (string, error) {
+	w.lock.RLock()
+	defer w.lock.RUnlock()
+
+	return w.buf.ReadString(delim)
+}
+
+// Bytes is a concurrent wrapper over the corresponding method of bytes.Buffer.
+func (w *ConcurrentBuffer) Bytes() []byte {
+	w.lock.RLock()
+	defer w.lock.RUnlock()
+
+	return w.buf.Bytes()
+}
+
+// String is a concurrent wrapper over the corresponding method of bytes.Buffer.
+func (w *ConcurrentBuffer) String() string {
+	w.lock.RLock()
+	defer w.lock.RUnlock()
+
+	return w.buf.String()
+}
+
+// Reset is a concurrent wrapper over the corresponding method of bytes.Buffer.
+func (w *ConcurrentBuffer) Reset() {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	w.buf.Reset()
+}
+
 func newTestChain(t *testing.T, f func(*config.Config), run bool) (*core.Blockchain, *server.Server, *network.Server) {
 	configPath := "../config/protocol.unit_testnet.single.yml"
 	cfg, err := config.LoadFile(configPath)
@@ -115,7 +169,7 @@ func newExecutorSuspended(t *testing.T) *executor {
 func newExecutorWithConfig(t *testing.T, needChain, runChain bool, f func(*config.Config)) *executor {
 	e := &executor{
 		CLI: newApp(),
-		Out: bytes.NewBuffer(nil),
+		Out: NewConcurrentBuffer(),
 		Err: bytes.NewBuffer(nil),
 		In:  bytes.NewBuffer(nil),
 	}
diff --git a/cli/multisig_test.go b/cli/multisig_test.go
index f673b0af5..654f131ce 100644
--- a/cli/multisig_test.go
+++ b/cli/multisig_test.go
@@ -14,6 +14,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/rpc/response/result"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/vm"
 	"github.com/stretchr/testify/require"
 )
@@ -64,6 +65,51 @@ func TestSignMultisigTx(t *testing.T) {
 	priv, err := keys.NewPrivateKey()
 	require.NoError(t, err)
 
+	t.Run("bad cases", func(t *testing.T) {
+		txPath := filepath.Join(tmpDir, "multisigtx.json")
+		t.Cleanup(func() {
+			os.Remove(txPath)
+		})
+		e.In.WriteString("pass\r")
+		e.Run(t, "neo-go", "wallet", "nep17", "transfer",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", wallet1Path, "--from", multisigAddr,
+			"--to", priv.Address(), "--token", "NEO", "--amount", "1",
+			"--out", txPath)
+
+		// missing wallet
+		e.RunWithError(t, "neo-go", "wallet", "sign")
+
+		// missing in
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--wallet", wallet2Path)
+
+		// missing address
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--wallet", wallet2Path,
+			"--in", txPath)
+
+		// invalid address
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--wallet", wallet2Path, "--address", util.Uint160{}.StringLE(),
+			"--in", txPath)
+
+		// invalid out
+		e.In.WriteString("pass\r")
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", wallet2Path, "--address", multisigAddr,
+			"--in", txPath, "--out", t.TempDir())
+
+		// invalid RPC endpoint
+		e.In.WriteString("pass\r")
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--rpc-endpoint", "http://not-an-address",
+			"--wallet", wallet2Path, "--address", multisigAddr,
+			"--in", txPath)
+	})
+
+	// Create transaction and save it for further multisigning.
 	txPath := filepath.Join(tmpDir, "multisigtx.json")
 	t.Cleanup(func() {
 		os.Remove(txPath)
@@ -90,12 +136,6 @@ func TestSignMultisigTx(t *testing.T) {
 		})
 	}
 
-	// missing address
-	e.RunWithError(t, "neo-go", "wallet", "sign",
-		"--rpc-endpoint", "http://"+e.RPC.Addr,
-		"--wallet", wallet2Path,
-		"--in", txPath, "--out", txPath)
-
 	t.Run("test invoke", func(t *testing.T) {
 		t.Run("missing file", func(t *testing.T) {
 			e.RunWithError(t, "neo-go", "util", "txdump")
@@ -124,6 +164,14 @@ func TestSignMultisigTx(t *testing.T) {
 		"--in", txPath, "--out", txPath)
 	e.checkTxPersisted(t)
 
+	t.Run("double-sign", func(t *testing.T) {
+		e.In.WriteString("pass\r")
+		e.RunWithError(t, "neo-go", "wallet", "sign",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", wallet2Path, "--address", multisigAddr,
+			"--in", txPath, "--out", txPath)
+	})
+
 	b, _ := e.Chain.GetGoverningTokenBalance(priv.GetScriptHash())
 	require.Equal(t, big.NewInt(1), b)
 	b, _ = e.Chain.GetGoverningTokenBalance(multisigHash)
diff --git a/cli/server/server.go b/cli/server/server.go
index 21156cec8..19d3a407a 100644
--- a/cli/server/server.go
+++ b/cli/server/server.go
@@ -393,11 +393,11 @@ func mkP2PNotary(config network.ServerConfig, chain *core.Blockchain, serv *netw
 func startServer(ctx *cli.Context) error {
 	cfg, err := getConfigFromContext(ctx)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 	log, err := handleLoggingParams(ctx, cfg.ApplicationConfiguration)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 
 	grace, cancel := context.WithCancel(newGraceContext())
@@ -407,7 +407,7 @@ func startServer(ctx *cli.Context) error {
 
 	chain, prometheus, pprof, err := initBCWithMetrics(cfg, log)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 
 	serv, err := network.NewServer(serverConfig, chain, chain.GetStateSyncModule(), log)
@@ -423,15 +423,15 @@ func startServer(ctx *cli.Context) error {
 
 	oracleSrv, err := mkOracle(serverConfig, chain, serv, log)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 	_, err = mkConsensus(serverConfig, chain, serv, log)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 	_, err = mkP2PNotary(serverConfig, chain, serv, log)
 	if err != nil {
-		return err
+		return cli.NewExitError(err, 1)
 	}
 	rpcServer := server.New(chain, cfg.ApplicationConfiguration.RPC, serv, oracleSrv, log)
 	errChan := make(chan error)
@@ -442,7 +442,7 @@ func startServer(ctx *cli.Context) error {
 	sighupCh := make(chan os.Signal, 1)
 	signal.Notify(sighupCh, syscall.SIGHUP)
 
-	fmt.Fprintln(ctx.App.Writer, logo())
+	fmt.Fprintln(ctx.App.Writer, Logo())
 	fmt.Fprintln(ctx.App.Writer, serv.UserAgent)
 	fmt.Fprintln(ctx.App.Writer)
 
@@ -517,7 +517,8 @@ func initBlockChain(cfg config.Config, log *zap.Logger) (*core.Blockchain, error
 	return chain, nil
 }
 
-func logo() string {
+// Logo returns Neo-Go logo.
+func Logo() string {
 	return `
     _   ____________        __________
    / | / / ____/ __ \      / ____/ __ \
diff --git a/cli/server/server_test.go b/cli/server/server_test.go
index 454076c75..7d0e8ebce 100644
--- a/cli/server/server_test.go
+++ b/cli/server/server_test.go
@@ -1,7 +1,9 @@
 package server
 
 import (
+	"encoding/binary"
 	"flag"
+	"io/ioutil"
 	"os"
 	"path/filepath"
 	"testing"
@@ -14,6 +16,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"github.com/urfave/cli"
 	"go.uber.org/zap"
+	"gopkg.in/yaml.v2"
 )
 
 // serverTestWD is the default working directory for server tests.
@@ -42,6 +45,18 @@ func TestHandleLoggingParams(t *testing.T) {
 	d := t.TempDir()
 	testLog := filepath.Join(d, "file.log")
 
+	t.Run("logdir is a file", func(t *testing.T) {
+		logfile := filepath.Join(d, "logdir")
+		require.NoError(t, ioutil.WriteFile(logfile, []byte{1, 2, 3}, os.ModePerm))
+		set := flag.NewFlagSet("flagSet", flag.ExitOnError)
+		ctx := cli.NewContext(cli.NewApp(), set, nil)
+		cfg := config.ApplicationConfiguration{
+			LogPath: filepath.Join(logfile, "file.log"),
+		}
+		_, err := handleLoggingParams(ctx, cfg)
+		require.Error(t, err)
+	})
+
 	t.Run("default", func(t *testing.T) {
 		set := flag.NewFlagSet("flagSet", flag.ExitOnError)
 		ctx := cli.NewContext(cli.NewApp(), set, nil)
@@ -83,6 +98,12 @@ func TestInitBCWithMetrics(t *testing.T) {
 	require.NoError(t, err)
 	logger, err := handleLoggingParams(ctx, cfg.ApplicationConfiguration)
 	require.NoError(t, err)
+
+	t.Run("bad store", func(t *testing.T) {
+		_, _, _, err = initBCWithMetrics(config.Config{}, logger)
+		require.Error(t, err)
+	})
+
 	chain, prometheus, pprof, err := initBCWithMetrics(cfg, logger)
 	require.NoError(t, err)
 	t.Cleanup(func() {
@@ -139,9 +160,10 @@ func TestRestoreDB(t *testing.T) {
 	require.NoError(t, err)
 	t.Cleanup(func() { require.NoError(t, os.Chdir(serverTestWD)) })
 
-	//dump first
+	// dump first
 	set := flag.NewFlagSet("flagSet", flag.ExitOnError)
-	set.String("config-path", filepath.Join(serverTestWD, "..", "..", "config"), "")
+	goodCfg := filepath.Join(serverTestWD, "..", "..", "config")
+	cfgPath := set.String("config-path", goodCfg, "")
 	set.Bool("privnet", true, "")
 	set.Bool("debug", true, "")
 	set.Int("start", 0, "")
@@ -152,7 +174,101 @@ func TestRestoreDB(t *testing.T) {
 	require.NoError(t, err)
 
 	// and then restore
-	set.String("in", testDump, "")
+	t.Run("invalid config", func(t *testing.T) {
+		*cfgPath = filepath.Join(serverTestWD, "..", "..", "config_invalid")
+		require.Error(t, restoreDB(ctx))
+	})
+	t.Run("invalid logger path", func(t *testing.T) {
+		badCfgDir := t.TempDir()
+		logfile := filepath.Join(badCfgDir, "logdir")
+		require.NoError(t, ioutil.WriteFile(logfile, []byte{1, 2, 3}, os.ModePerm))
+		cfg, err := config.LoadFile(filepath.Join(goodCfg, "protocol.privnet.yml"))
+		require.NoError(t, err, "could not load config")
+		cfg.ApplicationConfiguration.LogPath = filepath.Join(logfile, "file.log")
+		out, err := yaml.Marshal(cfg)
+		require.NoError(t, err)
+
+		badCfgPath := filepath.Join(badCfgDir, "protocol.privnet.yml")
+		require.NoError(t, ioutil.WriteFile(badCfgPath, out, os.ModePerm))
+
+		*cfgPath = badCfgDir
+		require.Error(t, restoreDB(ctx))
+
+		*cfgPath = goodCfg
+	})
+	t.Run("invalid bc config", func(t *testing.T) {
+		badCfgDir := t.TempDir()
+		cfg, err := config.LoadFile(filepath.Join(goodCfg, "protocol.privnet.yml"))
+		require.NoError(t, err, "could not load config")
+		cfg.ApplicationConfiguration.DBConfiguration.Type = ""
+		out, err := yaml.Marshal(cfg)
+		require.NoError(t, err)
+
+		badCfgPath := filepath.Join(badCfgDir, "protocol.privnet.yml")
+		require.NoError(t, ioutil.WriteFile(badCfgPath, out, os.ModePerm))
+
+		*cfgPath = badCfgDir
+		require.Error(t, restoreDB(ctx))
+
+		*cfgPath = goodCfg
+	})
+
+	in := set.String("in", testDump, "")
+	incremental := set.Bool("incremental", false, "")
+	t.Run("invalid in", func(t *testing.T) {
+		*in = "unknown-file"
+		require.Error(t, restoreDB(ctx))
+
+		*in = testDump
+	})
+	t.Run("corrupted in: invalid block count", func(t *testing.T) {
+		inPath := filepath.Join(t.TempDir(), "file3.acc")
+		require.NoError(t, ioutil.WriteFile(inPath, []byte{1, 2, 3}, // file is expected to start from uint32
+			os.ModePerm))
+		*in = inPath
+		require.Error(t, restoreDB(ctx))
+
+		*in = testDump
+	})
+	t.Run("corrupted in: corrupted block", func(t *testing.T) {
+		inPath := filepath.Join(t.TempDir(), "file3.acc")
+		b, err := ioutil.ReadFile(testDump)
+		require.NoError(t, err)
+		b[5] = 0xff // file is expected to start from uint32 (4 bytes) followed by the first block, so corrupt the first block bytes
+		require.NoError(t, ioutil.WriteFile(inPath, b, os.ModePerm))
+		*in = inPath
+		require.Error(t, restoreDB(ctx))
+
+		*in = testDump
+	})
+	t.Run("incremental dump", func(t *testing.T) {
+		inPath := filepath.Join(t.TempDir(), "file1_incremental.acc")
+		b, err := ioutil.ReadFile(testDump)
+		require.NoError(t, err)
+		start := make([]byte, 4)
+		t.Run("good", func(t *testing.T) {
+			binary.LittleEndian.PutUint32(start, 1) // start from the first block
+			require.NoError(t, ioutil.WriteFile(inPath, append(start, b...),
+				os.ModePerm))
+			*in = inPath
+			*incremental = true
+
+			require.NoError(t, restoreDB(ctx))
+		})
+		t.Run("dump is too high", func(t *testing.T) {
+			binary.LittleEndian.PutUint32(start, 2) // start from the second block
+			require.NoError(t, ioutil.WriteFile(inPath, append(start, b...),
+				os.ModePerm))
+			*in = inPath
+			*incremental = true
+
+			require.Error(t, restoreDB(ctx))
+		})
+
+		*in = testDump
+		*incremental = false
+	})
+
 	set.String("dump", saveDump, "")
 	require.NoError(t, restoreDB(ctx))
 }
diff --git a/cli/server_test.go b/cli/server_test.go
new file mode 100644
index 000000000..308ce98fc
--- /dev/null
+++ b/cli/server_test.go
@@ -0,0 +1,124 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/nspcc-dev/neo-go/cli/server"
+	"github.com/nspcc-dev/neo-go/pkg/config"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v2"
+)
+
+func TestServerStart(t *testing.T) {
+	tmpDir := t.TempDir()
+	goodCfg, err := config.LoadFile(filepath.Join("..", "config", "protocol.unit_testnet.yml"))
+	require.NoError(t, err, "could not load config")
+	ptr := &goodCfg
+	saveCfg := func(t *testing.T, f func(cfg *config.Config)) string {
+		cfg := *ptr
+		chainPath := filepath.Join(t.TempDir(), "neogotestchain")
+		cfg.ApplicationConfiguration.DBConfiguration.Type = "leveldb"
+		cfg.ApplicationConfiguration.DBConfiguration.LevelDBOptions.DataDirectoryPath = chainPath
+		f(&cfg)
+		out, err := yaml.Marshal(cfg)
+		require.NoError(t, err)
+
+		cfgPath := filepath.Join(tmpDir, "protocol.unit_testnet.yml")
+		require.NoError(t, ioutil.WriteFile(cfgPath, out, os.ModePerm))
+		t.Cleanup(func() {
+			require.NoError(t, os.Remove(cfgPath))
+		})
+		return cfgPath
+	}
+
+	baseCmd := []string{"neo-go", "node", "--unittest", "--config-path", tmpDir}
+	e := newExecutor(t, false)
+
+	t.Run("invalid config path", func(t *testing.T) {
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("bad logger config", func(t *testing.T) {
+		badConfigDir := t.TempDir()
+		logfile := filepath.Join(badConfigDir, "logdir")
+		require.NoError(t, ioutil.WriteFile(logfile, []byte{1, 2, 3}, os.ModePerm))
+		saveCfg(t, func(cfg *config.Config) {
+			cfg.ApplicationConfiguration.LogPath = filepath.Join(logfile, "file.log")
+		})
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("invalid storage", func(t *testing.T) {
+		saveCfg(t, func(cfg *config.Config) {
+			cfg.ApplicationConfiguration.DBConfiguration.Type = ""
+		})
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("stateroot service is on && StateRootInHeader=true", func(t *testing.T) {
+		saveCfg(t, func(cfg *config.Config) {
+			cfg.ApplicationConfiguration.StateRoot.Enabled = true
+			cfg.ProtocolConfiguration.StateRootInHeader = true
+		})
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("invalid Oracle config", func(t *testing.T) {
+		saveCfg(t, func(cfg *config.Config) {
+			cfg.ApplicationConfiguration.Oracle.Enabled = true
+			cfg.ApplicationConfiguration.Oracle.UnlockWallet.Path = "bad_orc_wallet.json"
+		})
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("invalid consensus config", func(t *testing.T) {
+		saveCfg(t, func(cfg *config.Config) {
+			cfg.ApplicationConfiguration.UnlockWallet.Path = "bad_consensus_wallet.json"
+		})
+		e.RunWithError(t, baseCmd...)
+	})
+	t.Run("invalid Notary config", func(t *testing.T) {
+		t.Run("malformed config", func(t *testing.T) {
+			saveCfg(t, func(cfg *config.Config) {
+				cfg.ProtocolConfiguration.P2PSigExtensions = false
+				cfg.ApplicationConfiguration.P2PNotary.Enabled = true
+			})
+			e.RunWithError(t, baseCmd...)
+		})
+		t.Run("invalid wallet", func(t *testing.T) {
+			saveCfg(t, func(cfg *config.Config) {
+				cfg.ProtocolConfiguration.P2PSigExtensions = true
+				cfg.ApplicationConfiguration.P2PNotary.Enabled = true
+				cfg.ApplicationConfiguration.P2PNotary.UnlockWallet.Path = "bad_notary_wallet.json"
+			})
+			e.RunWithError(t, baseCmd...)
+		})
+	})
+	t.Run("good", func(t *testing.T) {
+		saveCfg(t, func(cfg *config.Config) {})
+
+		go func() {
+			e.Run(t, baseCmd...)
+		}()
+
+		var line string
+		require.Eventually(t, func() bool {
+			line, err = e.Out.ReadString('\n')
+			if err != nil && err != io.EOF {
+				t.Fatalf(fmt.Sprintf("unexpected error while reading CLI output: %s", err))
+			}
+			return err == nil
+		}, 2*time.Second, 100*time.Millisecond)
+		lines := strings.Split(server.Logo(), "\n")
+		for _, expected := range lines {
+			// It should be regexp, so escape all backslashes.
+			expected = strings.ReplaceAll(expected, `\`, `\\`)
+			e.checkLine(t, line, expected)
+			line = e.getNextLine(t)
+		}
+		e.checkNextLine(t, "")
+		e.checkEOF(t)
+	})
+}
diff --git a/cli/smartcontract/manifest.go b/cli/smartcontract/manifest.go
index e7f5d4ee7..db315285a 100644
--- a/cli/smartcontract/manifest.go
+++ b/cli/smartcontract/manifest.go
@@ -29,12 +29,12 @@ func manifestAddGroup(ctx *cli.Context) error {
 
 	addr, err := flags.ParseAddress(ctx.String("account"))
 	if err != nil {
-		return cli.NewExitError(errors.New("address is missing"), 1)
+		return cli.NewExitError(fmt.Errorf("account is invalid or missing: %w", err), 1)
 	}
 
 	sender, err := flags.ParseAddress(ctx.String("sender"))
 	if err != nil {
-		return cli.NewExitError("invalid sender", 1)
+		return cli.NewExitError(fmt.Errorf("invalid sender: %w", err), 1)
 	}
 
 	nf, _, err := readNEFFile(ctx.String("nef"))
diff --git a/cli/smartcontract/smart_contract.go b/cli/smartcontract/smart_contract.go
index 607f56bc8..058e0eee5 100644
--- a/cli/smartcontract/smart_contract.go
+++ b/cli/smartcontract/smart_contract.go
@@ -653,18 +653,30 @@ func invokeWithArgs(ctx *cli.Context, acc *wallet.Account, wall *wallet.Wallet,
 		return sender, err
 	}
 
+	out := ctx.String("out")
 	resp, err = c.InvokeFunction(script, operation, params, cosigners)
 	if err != nil {
 		return sender, cli.NewExitError(err, 1)
 	}
-	if signAndPush && resp.State != "HALT" {
+	if resp.State != "HALT" {
 		errText := fmt.Sprintf("Warning: %s VM state returned from the RPC node: %s\n", resp.State, resp.FaultException)
-		if !ctx.Bool("force") {
-			return sender, cli.NewExitError(errText+". Use --force flag to send the transaction anyway.", 1)
+		action := "save"
+		process := "Saving"
+		if signAndPush {
+			if out != "" {
+				action += "and send"
+				process += "and sending"
+			} else {
+				action = "send"
+				process = "Sending"
+			}
 		}
-		fmt.Fprintln(ctx.App.Writer, errText+". Sending transaction...")
+		if !ctx.Bool("force") {
+			return sender, cli.NewExitError(errText+". Use --force flag to "+action+" the transaction anyway.", 1)
+		}
+		fmt.Fprintln(ctx.App.Writer, errText+". "+process+" transaction...")
 	}
-	if out := ctx.String("out"); out != "" {
+	if out != "" {
 		tx, err := c.CreateTxFromScript(resp.Script, acc, resp.GasConsumed+int64(sysgas), int64(gas), cosignersAccounts)
 		if err != nil {
 			return sender, cli.NewExitError(fmt.Errorf("failed to create tx: %w", err), 1)
diff --git a/cli/util_test.go b/cli/util_test.go
new file mode 100644
index 000000000..e845e7f37
--- /dev/null
+++ b/cli/util_test.go
@@ -0,0 +1,25 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/util"
+)
+
+func TestUtilConvert(t *testing.T) {
+	e := newExecutor(t, false)
+
+	e.Run(t, "neo-go", "util", "convert", util.Uint160{1, 2, 3}.StringLE())
+	e.checkNextLine(t, "f975")                                                                             // int to hex
+	e.checkNextLine(t, "\\+XU=")                                                                           // int to base64
+	e.checkNextLine(t, "NKuyBkoGdZZSLyPbJEetheRhMrGSCQx7YL")                                               // BE to address
+	e.checkNextLine(t, "NL1JGiyJXdTkvFksXbFxgLJcWLj8Ewe7HW")                                               // LE to address
+	e.checkNextLine(t, "Hex to String")                                                                    // hex to string
+	e.checkNextLine(t, "5753853598078696051256155186041784866529345536")                                   // hex to int
+	e.checkNextLine(t, "0102030000000000000000000000000000000000")                                         // swap endianness
+	e.checkNextLine(t, "Base64 to String")                                                                 // base64 to string
+	e.checkNextLine(t, "368753434210909009569191652203865891677393101439813372294890211308228051")         // base64 to bigint
+	e.checkNextLine(t, "30303030303030303030303030303030303030303030303030303030303030303030303330323031") // string to hex
+	e.checkNextLine(t, "MDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAwMDAzMDIwMQ==")                         // string to base64
+	e.checkEOF(t)
+}
diff --git a/cli/wallet/wallet.go b/cli/wallet/wallet.go
index 0d62f1840..391326de1 100644
--- a/cli/wallet/wallet.go
+++ b/cli/wallet/wallet.go
@@ -356,7 +356,11 @@ func convertWallet(ctx *cli.Context) error {
 		return cli.NewExitError(err, 1)
 	}
 
-	newWallet, err := wallet.NewWallet(ctx.String("out"))
+	out := ctx.String("out")
+	if len(out) == 0 {
+		return cli.NewExitError("missing out path", 1)
+	}
+	newWallet, err := wallet.NewWallet(out)
 	if err != nil {
 		return cli.NewExitError(err, 1)
 	}
@@ -375,7 +379,7 @@ func convertWallet(ctx *cli.Context) error {
 		newWallet.AddAccount(newAcc)
 	}
 	if err := newWallet.Save(); err != nil {
-		return cli.NewExitError(err, -1)
+		return cli.NewExitError(err, 1)
 	}
 	return nil
 }
@@ -605,7 +609,8 @@ func removeAccount(ctx *cli.Context) error {
 
 	if err := wall.RemoveAccount(acc.Address); err != nil {
 		return cli.NewExitError(fmt.Errorf("error on remove: %w", err), 1)
-	} else if err := wall.Save(); err != nil {
+	}
+	if err := wall.Save(); err != nil {
 		return cli.NewExitError(fmt.Errorf("error while saving wallet: %w", err), 1)
 	}
 	return nil
diff --git a/cli/wallet_test.go b/cli/wallet_test.go
index dc36cb5f0..504ffe3a9 100644
--- a/cli/wallet_test.go
+++ b/cli/wallet_test.go
@@ -3,7 +3,6 @@ package main
 import (
 	"encoding/hex"
 	"encoding/json"
-	"io/ioutil"
 	"math/big"
 	"path/filepath"
 	"strings"
@@ -14,6 +13,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/crypto/keys"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/smartcontract"
+	"github.com/nspcc-dev/neo-go/pkg/util"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 	"github.com/stretchr/testify/require"
 )
@@ -36,13 +36,34 @@ func TestWalletAccountRemove(t *testing.T) {
 	w, err := wallet.NewWalletFromFile(walletPath)
 	require.NoError(t, err)
 
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "remove")
+	})
+	t.Run("missing address", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "remove", "--wallet", walletPath)
+	})
+	t.Run("invalid address", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "remove", "--wallet", walletPath,
+			"--address", util.Uint160{}.StringLE())
+	})
+
 	addr := w.Accounts[0].Address
+	t.Run("askForConsent > no", func(t *testing.T) {
+		e.In.WriteString("no")
+		e.Run(t, "neo-go", "wallet", "remove", "--wallet", walletPath,
+			"--address", addr)
+		actual, err := wallet.NewWalletFromFile(walletPath)
+		require.NoError(t, err)
+		require.Equal(t, w, actual)
+	})
+
 	e.Run(t, "neo-go", "wallet", "remove", "--wallet", walletPath,
 		"--address", addr, "--force")
 
-	rawWallet, err := ioutil.ReadFile(walletPath)
+	actual, err := wallet.NewWalletFromFile(walletPath)
 	require.NoError(t, err)
-	require.NoError(t, json.Unmarshal(rawWallet, new(wallet.Wallet)))
+	require.Equal(t, 1, len(actual.Accounts))
+	require.Equal(t, w.Accounts[1], actual.Accounts[0])
 }
 
 func TestWalletChangePassword(t *testing.T) {
@@ -65,6 +86,12 @@ func TestWalletChangePassword(t *testing.T) {
 
 	addr1 := w.Accounts[0].Address
 	addr2 := w.Accounts[1].Address
+	t.Run("missing wallet path", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "change-password")
+	})
+	t.Run("EOF reading old password", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "change-password", "--wallet", walletPath)
+	})
 	t.Run("bad old password", func(t *testing.T) {
 		e.In.WriteString("ssap\r")
 		e.In.WriteString("aaa\r") // Pretend for the password to be fine.
@@ -112,9 +139,46 @@ func TestWalletChangePassword(t *testing.T) {
 }
 
 func TestWalletInit(t *testing.T) {
-	tmpDir := t.TempDir()
 	e := newExecutor(t, false)
 
+	t.Run("missing path", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "init")
+	})
+	t.Run("invalid path", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "init", "--wallet", t.TempDir())
+	})
+	t.Run("good: no account", func(t *testing.T) {
+		walletPath := filepath.Join(t.TempDir(), "wallet.json")
+		e.Run(t, "neo-go", "wallet", "init", "--wallet", walletPath)
+		w, err := wallet.NewWalletFromFile(walletPath)
+		require.NoError(t, err)
+		require.Equal(t, 0, len(w.Accounts))
+	})
+	t.Run("with account", func(t *testing.T) {
+		walletPath := filepath.Join(t.TempDir(), "wallet.json")
+		t.Run("missing acc name", func(t *testing.T) {
+			e.RunWithError(t, "neo-go", "wallet", "init", "--wallet", walletPath, "--account")
+		})
+		t.Run("missing pass", func(t *testing.T) {
+			e.In.WriteString("acc\r")
+			e.RunWithError(t, "neo-go", "wallet", "init", "--wallet", walletPath, "--account")
+		})
+		t.Run("missing second pass", func(t *testing.T) {
+			e.In.WriteString("acc\r")
+			e.In.WriteString("pass\r")
+			e.RunWithError(t, "neo-go", "wallet", "init", "--wallet", walletPath, "--account")
+		})
+		e.In.WriteString("acc\r")
+		e.In.WriteString("pass\r")
+		e.In.WriteString("pass\r")
+		e.Run(t, "neo-go", "wallet", "init", "--wallet", walletPath, "--account")
+		w, err := wallet.NewWalletFromFile(walletPath)
+		require.NoError(t, err)
+		require.Equal(t, 1, len(w.Accounts))
+		require.Equal(t, "acc", w.Accounts[0].Label)
+	})
+
+	tmpDir := t.TempDir()
 	walletPath := filepath.Join(tmpDir, "wallet.json")
 	e.Run(t, "neo-go", "wallet", "init", "--wallet", walletPath)
 
@@ -144,6 +208,12 @@ func TestWalletInit(t *testing.T) {
 		t.Run("stdin", func(t *testing.T) {
 			e.RunWithError(t, "neo-go", "wallet", "create", "--wallet", "-")
 		})
+		t.Run("passwords mismatch", func(t *testing.T) {
+			e.In.WriteString("testname\r")
+			e.In.WriteString("testpass\r")
+			e.In.WriteString("badpass\r")
+			e.RunWithError(t, "neo-go", "wallet", "create", "--wallet", walletPath)
+		})
 		e.In.WriteString("testname\r")
 		e.In.WriteString("testpass\r")
 		e.In.WriteString("testpass\r")
@@ -171,6 +241,9 @@ func TestWalletInit(t *testing.T) {
 
 	t.Run("Import", func(t *testing.T) {
 		t.Run("WIF", func(t *testing.T) {
+			t.Run("missing wallet", func(t *testing.T) {
+				e.RunWithError(t, "neo-go", "wallet", "import")
+			})
 			priv, err := keys.NewPrivateKey()
 			require.NoError(t, err)
 			e.In.WriteString("test_account\r")
@@ -194,6 +267,33 @@ func TestWalletInit(t *testing.T) {
 				e.RunWithError(t, "neo-go", "wallet", "import",
 					"--wallet", walletPath, "--wif", priv.WIF())
 			})
+
+			t.Run("contract", func(t *testing.T) {
+				priv, err = keys.NewPrivateKey()
+				require.NoError(t, err)
+
+				t.Run("invalid script", func(t *testing.T) {
+					e.In.WriteString("test_account_3\r")
+					e.In.WriteString("qwerty\r")
+					e.In.WriteString("qwerty\r")
+					e.RunWithError(t, "neo-go", "wallet", "import",
+						"--wallet", walletPath, "--wif", priv.WIF(), "--contract", "not-a-hex")
+				})
+
+				e.In.WriteString("test_account_3\r")
+				e.In.WriteString("qwerty\r")
+				e.In.WriteString("qwerty\r")
+				e.Run(t, "neo-go", "wallet", "import",
+					"--wallet", walletPath, "--wif", priv.WIF(), "--contract", "0a0b0c")
+
+				w, err := wallet.NewWalletFromFile(walletPath)
+				require.NoError(t, err)
+				t.Cleanup(w.Close)
+				acc := w.GetAccount(priv.GetScriptHash())
+				require.NotNil(t, acc)
+				require.Equal(t, "test_account_3", acc.Label)
+				require.NoError(t, acc.Decrypt("qwerty", w.Scrypt))
+			})
 		})
 		t.Run("EncryptedWIF", func(t *testing.T) {
 			acc, err := wallet.NewAccount()
@@ -218,12 +318,31 @@ func TestWalletInit(t *testing.T) {
 			require.NoError(t, actual.Decrypt("somepass", w.Scrypt))
 		})
 		t.Run("Multisig", func(t *testing.T) {
+			t.Run("missing wallet", func(t *testing.T) {
+				e.RunWithError(t, "neo-go", "wallet", "import-multisig")
+			})
+			t.Run("insufficient pubs", func(t *testing.T) {
+				e.RunWithError(t, "neo-go", "wallet", "import-multisig",
+					"--wallet", walletPath,
+					"--min", "2")
+			})
 			privs, pubs := generateKeys(t, 4)
-
 			cmd := []string{"neo-go", "wallet", "import-multisig",
 				"--wallet", walletPath,
-				"--wif", privs[0].WIF(),
 				"--min", "2"}
+			t.Run("invalid pub encoding", func(t *testing.T) {
+				e.RunWithError(t, append(cmd, hex.EncodeToString(pubs[1].Bytes()),
+					hex.EncodeToString(pubs[1].Bytes()),
+					hex.EncodeToString(pubs[2].Bytes()),
+					"not-a-pub")...)
+			})
+			t.Run("missing WIF", func(t *testing.T) {
+				e.RunWithError(t, append(cmd, hex.EncodeToString(pubs[0].Bytes()),
+					hex.EncodeToString(pubs[1].Bytes()),
+					hex.EncodeToString(pubs[2].Bytes()),
+					hex.EncodeToString(pubs[3].Bytes()))...)
+			})
+			cmd = append(cmd, "--wif", privs[0].WIF())
 			t.Run("InvalidPublicKeys", func(t *testing.T) {
 				e.In.WriteString("multiacc\r")
 				e.In.WriteString("multipass\r")
@@ -253,6 +372,16 @@ func TestWalletInit(t *testing.T) {
 			require.NotNil(t, actual)
 			require.NoError(t, actual.Decrypt("multipass", w.Scrypt))
 			require.Equal(t, script, actual.Contract.Script)
+
+			t.Run("double-import", func(t *testing.T) {
+				e.In.WriteString("multiacc\r")
+				e.In.WriteString("multipass\r")
+				e.In.WriteString("multipass\r")
+				e.RunWithError(t, append(cmd, hex.EncodeToString(pubs[0].Bytes()),
+					hex.EncodeToString(pubs[1].Bytes()),
+					hex.EncodeToString(pubs[2].Bytes()),
+					hex.EncodeToString(pubs[3].Bytes()))...)
+			})
 		})
 	})
 }
@@ -260,6 +389,13 @@ func TestWalletInit(t *testing.T) {
 func TestWalletExport(t *testing.T) {
 	e := newExecutor(t, false)
 
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "export")
+	})
+	t.Run("invalid address", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "export",
+			"--wallet", validatorWallet, "not-an-address")
+	})
 	t.Run("Encrypted", func(t *testing.T) {
 		e.Run(t, "neo-go", "wallet", "export",
 			"--wallet", validatorWallet, validatorAddr)
@@ -274,6 +410,15 @@ func TestWalletExport(t *testing.T) {
 			e.RunWithError(t, "neo-go", "wallet", "export",
 				"--wallet", validatorWallet, "--decrypt")
 		})
+		t.Run("EOF reading password", func(t *testing.T) {
+			e.RunWithError(t, "neo-go", "wallet", "export",
+				"--wallet", validatorWallet, "--decrypt", validatorAddr)
+		})
+		t.Run("invalid password", func(t *testing.T) {
+			e.In.WriteString("invalid_pass\r")
+			e.RunWithError(t, "neo-go", "wallet", "export",
+				"--wallet", validatorWallet, "--decrypt", validatorAddr)
+		})
 		e.In.WriteString("one\r")
 		e.Run(t, "neo-go", "wallet", "export",
 			"--wallet", validatorWallet, "--decrypt", validatorAddr)
@@ -283,9 +428,39 @@ func TestWalletExport(t *testing.T) {
 	})
 }
 
-func TestClaimGas(t *testing.T) {
+func TestWalletClaimGas(t *testing.T) {
 	e := newExecutor(t, true)
 
+	t.Run("missing wallet path", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "claim",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--address", testWalletAccount)
+	})
+	t.Run("missing address", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "claim",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", testWalletPath)
+	})
+	t.Run("invalid address", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "claim",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", testWalletPath,
+			"--address", util.Uint160{}.StringLE())
+	})
+	t.Run("missing endpoint", func(t *testing.T) {
+		e.In.WriteString("testpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "claim",
+			"--wallet", testWalletPath,
+			"--address", testWalletAccount)
+	})
+	t.Run("insufficient funds", func(t *testing.T) {
+		e.In.WriteString("testpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "claim",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", testWalletPath,
+			"--address", testWalletAccount)
+	})
+
 	args := []string{
 		"neo-go", "wallet", "nep17", "multitransfer",
 		"--rpc-endpoint", "http://" + e.RPC.Addr,
@@ -326,7 +501,7 @@ func TestClaimGas(t *testing.T) {
 	}
 }
 
-func TestImportDeployed(t *testing.T) {
+func TestWalletImportDeployed(t *testing.T) {
 	tmpDir := t.TempDir()
 	e := newExecutor(t, true)
 	h := deployVerifyContract(t, e)
@@ -337,15 +512,43 @@ func TestImportDeployed(t *testing.T) {
 	priv, err := keys.NewPrivateKey()
 	require.NoError(t, err)
 
-	// missing contract sh
-	e.RunWithError(t, "neo-go", "wallet", "import-deployed",
-		"--rpc-endpoint", "http://"+e.RPC.Addr,
-		"--wallet", walletPath, "--wif", priv.WIF())
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed")
+	})
+	t.Run("missing contract sh", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--wallet", walletPath)
+	})
+	t.Run("missing WIF", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--wallet", walletPath, "--contract", h.StringLE())
+	})
+	t.Run("missing endpoint", func(t *testing.T) {
+		e.In.WriteString("acc\rpass\rpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--wallet", walletPath, "--contract", h.StringLE(),
+			"--wif", priv.WIF())
+	})
+	t.Run("unknown contract", func(t *testing.T) {
+		e.In.WriteString("acc\rpass\rpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", walletPath, "--contract", util.Uint160{}.StringLE(),
+			"--wif", priv.WIF())
+	})
+	t.Run("no `verify` method", func(t *testing.T) {
+		badH := deployNNSContract(t, e) // wrong contract with no `verify` method
+		e.In.WriteString("acc\rpass\rpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", walletPath, "--contract", badH.StringLE(),
+			"--wif", priv.WIF())
+	})
 
 	e.In.WriteString("acc\rpass\rpass\r")
 	e.Run(t, "neo-go", "wallet", "import-deployed",
 		"--rpc-endpoint", "http://"+e.RPC.Addr,
-		"--wallet", walletPath, "--wif", priv.WIF(),
+		"--wallet", walletPath, "--wif", priv.WIF(), "--name", "my_acc",
 		"--contract", h.StringLE())
 
 	w, err := wallet.NewWalletFromFile(walletPath)
@@ -358,6 +561,14 @@ func TestImportDeployed(t *testing.T) {
 	require.Equal(t, address.Uint160ToString(h), contractAddr)
 	require.True(t, w.Accounts[0].Contract.Deployed)
 
+	t.Run("re-importing", func(t *testing.T) {
+		e.In.WriteString("acc\rpass\rpass\r")
+		e.RunWithError(t, "neo-go", "wallet", "import-deployed",
+			"--rpc-endpoint", "http://"+e.RPC.Addr,
+			"--wallet", walletPath, "--wif", priv.WIF(), "--name", "my_acc",
+			"--contract", h.StringLE())
+	})
+
 	t.Run("Sign", func(t *testing.T) {
 		e.In.WriteString("one\r")
 		e.Run(t, "neo-go", "wallet", "nep17", "multitransfer",
@@ -389,6 +600,9 @@ func TestImportDeployed(t *testing.T) {
 func TestWalletDump(t *testing.T) {
 	e := newExecutor(t, false)
 
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "dump")
+	})
 	cmd := []string{"neo-go", "wallet", "dump", "--wallet", testWalletPath}
 	e.Run(t, cmd...)
 	rawStr := strings.TrimSpace(e.Out.String())
@@ -399,6 +613,9 @@ func TestWalletDump(t *testing.T) {
 
 	t.Run("with decrypt", func(t *testing.T) {
 		cmd = append(cmd, "--decrypt")
+		t.Run("EOF reading password", func(t *testing.T) {
+			e.RunWithError(t, cmd...)
+		})
 		t.Run("invalid password", func(t *testing.T) {
 			e.In.WriteString("invalidpass\r")
 			e.RunWithError(t, cmd...)
@@ -414,8 +631,11 @@ func TestWalletDump(t *testing.T) {
 	})
 }
 
-func TestDumpKeys(t *testing.T) {
+func TestWalletDumpKeys(t *testing.T) {
 	e := newExecutor(t, false)
+	t.Run("missing wallet", func(t *testing.T) {
+		e.RunWithError(t, "neo-go", "wallet", "dump-keys")
+	})
 	cmd := []string{"neo-go", "wallet", "dump-keys", "--wallet", validatorWallet}
 	pubRegex := "^0[23][a-hA-H0-9]{64}$"
 	t.Run("all", func(t *testing.T) {
@@ -432,6 +652,10 @@ func TestDumpKeys(t *testing.T) {
 		e.checkNextLine(t, pubRegex)
 		e.checkEOF(t)
 	})
+	t.Run("unknown address", func(t *testing.T) {
+		cmd := append(cmd, "--address", util.Uint160{}.StringLE())
+		e.RunWithError(t, cmd...)
+	})
 	t.Run("simple signature", func(t *testing.T) {
 		cmd := append(cmd, "--address", "Nhfg3TbpwogLvDGVvAvqyThbsHgoSUKwtn")
 		e.Run(t, cmd...)
@@ -467,8 +691,16 @@ func TestWalletConvert(t *testing.T) {
 	t.Run("missing wallet", func(t *testing.T) {
 		e.RunWithError(t, cmd...)
 	})
+	cmd = append(cmd, "--wallet", "testdata/wallets/testwallet_NEO2.json")
+	t.Run("missing out path", func(t *testing.T) {
+		e.RunWithError(t, cmd...)
+	})
+	t.Run("invalid out path", func(t *testing.T) {
+		dir := t.TempDir()
+		e.RunWithError(t, append(cmd, "--out", dir)...)
+	})
 
-	cmd = append(cmd, "--wallet", "testdata/wallets/testwallet_NEO2.json", "--out", outPath)
+	cmd = append(cmd, "--out", outPath)
 	t.Run("invalid password", func(t *testing.T) {
 		// missing password
 		e.RunWithError(t, cmd...)
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 000000000..dff9fb2bf
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,11 @@
+codecov:
+  require_ci_to_pass: no # We have several CI jobs that upload codecov results,
+                         # and sometimes some of them may fail, it's OK.
+coverage:
+  status:
+    project:
+      default: # This can be anything, but it needs to exist as the name
+        if_ci_failed: error #success, failure, error, ignore
+        only_pulls: false
+comment:
+  after_n_builds: 1