package agent import ( "bytes" "errors" "fmt" "log" "net" "net/http" "net/http/httptest" "os" "os/exec" "strings" "sync" "testing" "time" docker "github.com/fsouza/go-dockerclient" "github.com/hashicorp/consul/api" "github.com/hashicorp/consul/testutil" "github.com/hashicorp/consul/types" ) type MockNotify struct { state map[types.CheckID]string updates map[types.CheckID]int output map[types.CheckID]string // A guard to protect an access to the internal attributes // of the notification mock in order to prevent panics // raised by the race conditions detector. mu sync.RWMutex } func (m *MockNotify) UpdateCheck(id types.CheckID, status, output string) { m.mu.Lock() defer m.mu.Unlock() m.state[id] = status old := m.updates[id] m.updates[id] = old + 1 m.output[id] = output } // State returns the state of the specified health-check. func (m *MockNotify) State(id types.CheckID) string { m.mu.RLock() defer m.mu.RUnlock() return m.state[id] } // Updates returns the count of updates of the specified health-check. func (m *MockNotify) Updates(id types.CheckID) int { m.mu.RLock() defer m.mu.RUnlock() return m.updates[id] } // Output returns an output string of the specified health-check. func (m *MockNotify) Output(id types.CheckID) string { m.mu.RLock() defer m.mu.RUnlock() return m.output[id] } func expectStatus(t *testing.T, script, status string) { mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckMonitor{ Notify: mock, CheckID: types.CheckID("foo"), Script: script, Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if err := testutil.WaitForResult(func() (bool, error) { // Should have at least 2 updates if mock.Updates("foo") < 2 { return false, fmt.Errorf("should have 2 updates %v", mock.updates) } if mock.State("foo") != status { return false, fmt.Errorf("should be %v %v", status, mock.state) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckMonitor_Passing(t *testing.T) { t.Parallel() expectStatus(t, "exit 0", api.HealthPassing) } func TestCheckMonitor_Warning(t *testing.T) { t.Parallel() expectStatus(t, "exit 1", api.HealthWarning) } func TestCheckMonitor_Critical(t *testing.T) { t.Parallel() expectStatus(t, "exit 2", api.HealthCritical) } func TestCheckMonitor_BadCmd(t *testing.T) { t.Parallel() expectStatus(t, "foobarbaz", api.HealthCritical) } func TestCheckMonitor_Timeout(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckMonitor{ Notify: mock, CheckID: types.CheckID("foo"), Script: "sleep 1 && exit 0", Interval: 10 * time.Millisecond, Timeout: 5 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) // Should have at least 2 updates if mock.Updates("foo") < 2 { t.Fatalf("should have at least 2 updates %v", mock.updates) } if mock.State("foo") != "critical" { t.Fatalf("should be critical %v", mock.state) } } func TestCheckMonitor_RandomStagger(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckMonitor{ Notify: mock, CheckID: types.CheckID("foo"), Script: "exit 0", Interval: 25 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) // Should have at least 1 update if mock.Updates("foo") < 1 { t.Fatalf("should have 1 or more updates %v", mock.updates) } if mock.State("foo") != api.HealthPassing { t.Fatalf("should be %v %v", api.HealthPassing, mock.state) } } func TestCheckMonitor_LimitOutput(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckMonitor{ Notify: mock, CheckID: types.CheckID("foo"), Script: "od -N 81920 /dev/urandom", Interval: 25 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) // Allow for extra bytes for the truncation message if len(mock.Output("foo")) > CheckBufSize+100 { t.Fatalf("output size is too long") } } func TestCheckTTL(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckTTL{ Notify: mock, CheckID: types.CheckID("foo"), TTL: 100 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) check.SetStatus(api.HealthPassing, "test-output") if mock.Updates("foo") != 1 { t.Fatalf("should have 1 updates %v", mock.updates) } if mock.State("foo") != api.HealthPassing { t.Fatalf("should be passing %v", mock.state) } // Ensure we don't fail early time.Sleep(75 * time.Millisecond) if mock.Updates("foo") != 1 { t.Fatalf("should have 1 updates %v", mock.updates) } // Wait for the TTL to expire time.Sleep(75 * time.Millisecond) if mock.Updates("foo") != 2 { t.Fatalf("should have 2 updates %v", mock.updates) } if mock.State("foo") != api.HealthCritical { t.Fatalf("should be critical %v", mock.state) } if !strings.Contains(mock.Output("foo"), "test-output") { t.Fatalf("should have retained output %v", mock.output) } } func mockHTTPServer(responseCode int) *httptest.Server { mux := http.NewServeMux() mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { // Body larger than 4k limit body := bytes.Repeat([]byte{'a'}, 2*CheckBufSize) w.WriteHeader(responseCode) w.Write(body) return }) return httptest.NewServer(mux) } func mockTLSHTTPServer(responseCode int) *httptest.Server { mux := http.NewServeMux() mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { // Body larger than 4k limit body := bytes.Repeat([]byte{'a'}, 2*CheckBufSize) w.WriteHeader(responseCode) w.Write(body) return }) return httptest.NewTLSServer(mux) } func expectHTTPStatus(t *testing.T, url string, status string) { mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckHTTP{ Notify: mock, CheckID: types.CheckID("foo"), HTTP: url, Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if err := testutil.WaitForResult(func() (bool, error) { // Should have at least 2 updates if mock.Updates("foo") < 2 { return false, fmt.Errorf("should have 2 updates %v", mock.updates) } if mock.State("foo") != status { return false, fmt.Errorf("should be %v %v", status, mock.state) } // Allow slightly more data than CheckBufSize, for the header if n := len(mock.Output("foo")); n > (CheckBufSize + 256) { return false, fmt.Errorf("output too long: %d (%d-byte limit)", n, CheckBufSize) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckHTTPCritical(t *testing.T) { t.Parallel() // var server *httptest.Server server := mockHTTPServer(150) fmt.Println(server.URL) expectHTTPStatus(t, server.URL, api.HealthCritical) server.Close() // 2xx - 1 server = mockHTTPServer(199) expectHTTPStatus(t, server.URL, api.HealthCritical) server.Close() // 2xx + 1 server = mockHTTPServer(300) expectHTTPStatus(t, server.URL, api.HealthCritical) server.Close() server = mockHTTPServer(400) expectHTTPStatus(t, server.URL, api.HealthCritical) server.Close() server = mockHTTPServer(500) expectHTTPStatus(t, server.URL, api.HealthCritical) server.Close() } func TestCheckHTTPPassing(t *testing.T) { t.Parallel() var server *httptest.Server server = mockHTTPServer(200) expectHTTPStatus(t, server.URL, api.HealthPassing) server.Close() server = mockHTTPServer(201) expectHTTPStatus(t, server.URL, api.HealthPassing) server.Close() server = mockHTTPServer(250) expectHTTPStatus(t, server.URL, api.HealthPassing) server.Close() server = mockHTTPServer(299) expectHTTPStatus(t, server.URL, api.HealthPassing) server.Close() } func TestCheckHTTPWarning(t *testing.T) { t.Parallel() server := mockHTTPServer(429) expectHTTPStatus(t, server.URL, api.HealthWarning) server.Close() } func mockSlowHTTPServer(responseCode int, sleep time.Duration) *httptest.Server { mux := http.NewServeMux() mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { time.Sleep(sleep) w.WriteHeader(responseCode) return }) return httptest.NewServer(mux) } func TestCheckHTTPTimeout(t *testing.T) { t.Parallel() server := mockSlowHTTPServer(200, 10*time.Millisecond) defer server.Close() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckHTTP{ Notify: mock, CheckID: types.CheckID("bar"), HTTP: server.URL, Timeout: 5 * time.Millisecond, Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if err := testutil.WaitForResult(func() (bool, error) { // Should have at least 2 updates if mock.updates["bar"] < 2 { return false, fmt.Errorf("should have at least 2 updates %v", mock.updates) } if mock.state["bar"] != api.HealthCritical { return false, fmt.Errorf("should be critical %v", mock.state) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckHTTP_disablesKeepAlives(t *testing.T) { t.Parallel() check := &CheckHTTP{ CheckID: types.CheckID("foo"), HTTP: "http://foo.bar/baz", Interval: 10 * time.Second, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if !check.httpClient.Transport.(*http.Transport).DisableKeepAlives { t.Fatalf("should have disabled keepalives") } } func TestCheckHTTP_TLSSkipVerify_defaultFalse(t *testing.T) { t.Parallel() check := &CheckHTTP{ CheckID: "foo", HTTP: "https://foo.bar/baz", Interval: 10 * time.Second, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if check.httpClient.Transport.(*http.Transport).TLSClientConfig.InsecureSkipVerify { t.Fatalf("should default to false") } } func TestCheckHTTP_TLSSkipVerify_true_pass(t *testing.T) { t.Parallel() server := mockTLSHTTPServer(200) defer server.Close() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckHTTP{ Notify: mock, CheckID: types.CheckID("skipverify_true"), HTTP: server.URL, Interval: 5 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), TLSSkipVerify: true, } check.Start() defer check.Stop() if !check.httpClient.Transport.(*http.Transport).TLSClientConfig.InsecureSkipVerify { t.Fatalf("should be true") } if err := testutil.WaitForResult(func() (bool, error) { if mock.state["skipverify_true"] != api.HealthPassing { return false, fmt.Errorf("should be passing %v", mock.state) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckHTTP_TLSSkipVerify_true_fail(t *testing.T) { t.Parallel() server := mockTLSHTTPServer(500) defer server.Close() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckHTTP{ Notify: mock, CheckID: types.CheckID("skipverify_true"), HTTP: server.URL, Interval: 5 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), TLSSkipVerify: true, } check.Start() defer check.Stop() if !check.httpClient.Transport.(*http.Transport).TLSClientConfig.InsecureSkipVerify { t.Fatalf("should be true") } if err := testutil.WaitForResult(func() (bool, error) { if mock.state["skipverify_true"] != api.HealthCritical { return false, fmt.Errorf("should be critical %v", mock.state) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckHTTP_TLSSkipVerify_false(t *testing.T) { t.Parallel() server := mockTLSHTTPServer(200) defer server.Close() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckHTTP{ Notify: mock, CheckID: types.CheckID("skipverify_false"), HTTP: server.URL, Interval: 100 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), TLSSkipVerify: false, } check.Start() defer check.Stop() if check.httpClient.Transport.(*http.Transport).TLSClientConfig.InsecureSkipVerify { t.Fatalf("should be false") } if err := testutil.WaitForResult(func() (bool, error) { // This should fail due to an invalid SSL cert if mock.state["skipverify_false"] != api.HealthCritical { return false, fmt.Errorf("should be critical %v", mock.state) } if !strings.Contains(mock.output["skipverify_false"], "certificate signed by unknown authority") { return false, fmt.Errorf("should fail with certificate error %v", mock.output) } return true, nil }); err != nil { t.Fatal(err) } } func mockTCPServer(network string) net.Listener { var ( addr string ) if network == `tcp6` { addr = `[::1]:0` } else { addr = `127.0.0.1:0` } listener, err := net.Listen(network, addr) if err != nil { panic(err) } return listener } func expectTCPStatus(t *testing.T, tcp string, status string) { mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckTCP{ Notify: mock, CheckID: types.CheckID("foo"), TCP: tcp, Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), } check.Start() defer check.Stop() if err := testutil.WaitForResult(func() (bool, error) { // Should have at least 2 updates if mock.Updates("foo") < 2 { return false, fmt.Errorf("should have 2 updates %v", mock.updates) } if mock.State("foo") != status { return false, fmt.Errorf("should be %v %v", status, mock.state) } return true, nil }); err != nil { t.Fatal(err) } } func TestCheckTCPCritical(t *testing.T) { t.Parallel() var ( tcpServer net.Listener ) tcpServer = mockTCPServer(`tcp`) expectTCPStatus(t, `127.0.0.1:0`, api.HealthCritical) tcpServer.Close() } func TestCheckTCPPassing(t *testing.T) { t.Parallel() var ( tcpServer net.Listener ) tcpServer = mockTCPServer(`tcp`) expectTCPStatus(t, tcpServer.Addr().String(), api.HealthPassing) tcpServer.Close() tcpServer = mockTCPServer(`tcp6`) expectTCPStatus(t, tcpServer.Addr().String(), api.HealthPassing) tcpServer.Close() } // A fake docker client to test happy path scenario type fakeDockerClientWithNoErrors struct { } func (d *fakeDockerClientWithNoErrors) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithNoErrors) StartExec(id string, opts docker.StartExecOptions) error { fmt.Fprint(opts.OutputStream, "output") return nil } func (d *fakeDockerClientWithNoErrors) InspectExec(id string) (*docker.ExecInspect, error) { return &docker.ExecInspect{ ID: "123", ExitCode: 0, }, nil } // A fake docker client to test truncation of output type fakeDockerClientWithLongOutput struct { } func (d *fakeDockerClientWithLongOutput) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithLongOutput) StartExec(id string, opts docker.StartExecOptions) error { b, _ := exec.Command("od", "-N", "81920", "/dev/urandom").Output() fmt.Fprint(opts.OutputStream, string(b)) return nil } func (d *fakeDockerClientWithLongOutput) InspectExec(id string) (*docker.ExecInspect, error) { return &docker.ExecInspect{ ID: "123", ExitCode: 0, }, nil } // A fake docker client to test non-zero exit codes from exec invocation type fakeDockerClientWithExecNonZeroExitCode struct { } func (d *fakeDockerClientWithExecNonZeroExitCode) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithExecNonZeroExitCode) StartExec(id string, opts docker.StartExecOptions) error { return nil } func (d *fakeDockerClientWithExecNonZeroExitCode) InspectExec(id string) (*docker.ExecInspect, error) { return &docker.ExecInspect{ ID: "123", ExitCode: 127, }, nil } // A fake docker client to test exit code which result into Warning type fakeDockerClientWithExecExitCodeOne struct { } func (d *fakeDockerClientWithExecExitCodeOne) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithExecExitCodeOne) StartExec(id string, opts docker.StartExecOptions) error { fmt.Fprint(opts.OutputStream, "output") return nil } func (d *fakeDockerClientWithExecExitCodeOne) InspectExec(id string) (*docker.ExecInspect, error) { return &docker.ExecInspect{ ID: "123", ExitCode: 1, }, nil } // A fake docker client to simulate create exec failing type fakeDockerClientWithCreateExecFailure struct { } func (d *fakeDockerClientWithCreateExecFailure) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return nil, errors.New("Exec Creation Failed") } func (d *fakeDockerClientWithCreateExecFailure) StartExec(id string, opts docker.StartExecOptions) error { return errors.New("Exec doesn't exist") } func (d *fakeDockerClientWithCreateExecFailure) InspectExec(id string) (*docker.ExecInspect, error) { return nil, errors.New("Exec doesn't exist") } // A fake docker client to simulate start exec failing type fakeDockerClientWithStartExecFailure struct { } func (d *fakeDockerClientWithStartExecFailure) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithStartExecFailure) StartExec(id string, opts docker.StartExecOptions) error { return errors.New("Couldn't Start Exec") } func (d *fakeDockerClientWithStartExecFailure) InspectExec(id string) (*docker.ExecInspect, error) { return nil, errors.New("Exec doesn't exist") } // A fake docker client to test exec info query failures type fakeDockerClientWithExecInfoErrors struct { } func (d *fakeDockerClientWithExecInfoErrors) CreateExec(opts docker.CreateExecOptions) (*docker.Exec, error) { return &docker.Exec{ID: "123"}, nil } func (d *fakeDockerClientWithExecInfoErrors) StartExec(id string, opts docker.StartExecOptions) error { return nil } func (d *fakeDockerClientWithExecInfoErrors) InspectExec(id string) (*docker.ExecInspect, error) { return nil, errors.New("Unable to query exec info") } func expectDockerCheckStatus(t *testing.T, dockerClient DockerClient, status string, output string) { mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckDocker{ Notify: mock, CheckID: types.CheckID("foo"), Script: "/health.sh", DockerContainerID: "54432bad1fc7", Shell: "/bin/sh", Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), dockerClient: dockerClient, } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) // Should have at least 2 updates if mock.Updates("foo") < 2 { t.Fatalf("should have 2 updates %v", mock.updates) } if mock.State("foo") != status { t.Fatalf("should be %v %v", status, mock.state) } if mock.Output("foo") != output { t.Fatalf("should be %v %v", output, mock.output) } } func TestDockerCheckWhenExecReturnsSuccessExitCode(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithNoErrors{}, api.HealthPassing, "output") } func TestDockerCheckWhenExecCreationFails(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithCreateExecFailure{}, api.HealthCritical, "Unable to create Exec, error: Exec Creation Failed") } func TestDockerCheckWhenExitCodeIsNonZero(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithExecNonZeroExitCode{}, api.HealthCritical, "") } func TestDockerCheckWhenExitCodeIsone(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithExecExitCodeOne{}, api.HealthWarning, "output") } func TestDockerCheckWhenExecStartFails(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithStartExecFailure{}, api.HealthCritical, "Unable to start Exec: Couldn't Start Exec") } func TestDockerCheckWhenExecInfoFails(t *testing.T) { t.Parallel() expectDockerCheckStatus(t, &fakeDockerClientWithExecInfoErrors{}, api.HealthCritical, "Unable to inspect Exec: Unable to query exec info") } func TestDockerCheckDefaultToSh(t *testing.T) { t.Parallel() os.Setenv("SHELL", "") mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckDocker{ Notify: mock, CheckID: types.CheckID("foo"), Script: "/health.sh", DockerContainerID: "54432bad1fc7", Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), dockerClient: &fakeDockerClientWithNoErrors{}, } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) if check.Shell != "/bin/sh" { t.Fatalf("Shell should be: %v , actual: %v", "/bin/sh", check.Shell) } } func TestDockerCheckUseShellFromEnv(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } os.Setenv("SHELL", "/bin/bash") check := &CheckDocker{ Notify: mock, CheckID: types.CheckID("foo"), Script: "/health.sh", DockerContainerID: "54432bad1fc7", Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), dockerClient: &fakeDockerClientWithNoErrors{}, } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) if check.Shell != "/bin/bash" { t.Fatalf("Shell should be: %v , actual: %v", "/bin/bash", check.Shell) } os.Setenv("SHELL", "") } func TestDockerCheckTruncateOutput(t *testing.T) { t.Parallel() mock := &MockNotify{ state: make(map[types.CheckID]string), updates: make(map[types.CheckID]int), output: make(map[types.CheckID]string), } check := &CheckDocker{ Notify: mock, CheckID: types.CheckID("foo"), Script: "/health.sh", DockerContainerID: "54432bad1fc7", Shell: "/bin/sh", Interval: 10 * time.Millisecond, Logger: log.New(os.Stderr, "", log.LstdFlags), dockerClient: &fakeDockerClientWithLongOutput{}, } check.Start() defer check.Stop() time.Sleep(50 * time.Millisecond) // Allow for extra bytes for the truncation message if len(mock.Output("foo")) > CheckBufSize+100 { t.Fatalf("output size is too long") } }