feat: support user provided loggers

internal/ui/output.go

@@ -58,3 +58,10 @@ func NewDefaultOutput(logLevel slog.Level, jsonFormat bool) *Output {
 
 	return NewOutput(logger, printer, interactive, true)
 }
+
+func NewDefaultOutputWithLogger(logger *slog.Logger) *Output {
+	printer := NewDefaultPrinter()
+	interactive := isatty.IsTerminal(os.Stdin.Fd())
+
+	return NewOutput(logger, printer, interactive, true)
+}

pkg/f1/f1.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"log/slog"
 	"os"
 	"os/signal"
 	"syscall"
@@ -32,7 +33,7 @@ type F1 struct {
 	settings  envsettings.Settings
 }
 
-// Instantiates a new instance of an F1 CLI.
+// New instantiates a new instance of an F1 CLI.
 func New() *F1 {
 	settings := envsettings.Get()
 
@@ -44,6 +45,17 @@ func New() *F1 {
 	}
 }
 
+// WithLogger allows specifying logger to be used for all internal and scenario logs
+//
+// This will disable the LOG_LEVEL and LOG_FORMAT options, as they only relate to the built-in
+// logger.
+//
+// The logger will be used for non-interactive output, file logs or when `--verbose` is specified.
+func (f *F1) WithLogger(logger *slog.Logger) *F1 {
+	f.output = ui.NewDefaultOutputWithLogger(logger)
+	return f
+}
+
 // Registers a new test scenario with the given name. This is the name used when running
 // load test scenarios. For example, calling the function with the following arguments:
 //

pkg/f1/f1_stage_test.go

@@ -1,7 +1,10 @@
 package f1_test
 
 import (
+	"bytes"
+	"fmt"
 	"os"
+	"strings"
 	"sync/atomic"
 	"syscall"
 	"testing"
@@ -11,21 +14,21 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.uber.org/goleak"
 
+	"github.com/form3tech-oss/f1/v2/internal/log"
 	"github.com/form3tech-oss/f1/v2/pkg/f1"
 	f1_testing "github.com/form3tech-oss/f1/v2/pkg/f1/testing"
 )
 
 type f1Stage struct {
-	t       *testing.T
-	assert  *assert.Assertions
-	require *require.Assertions
-
-	f1       *f1.F1
-	errCh    chan error
-	scenario string
-	runCount atomic.Uint32
-
 	executeErr error
+	t          *testing.T
+	assert     *assert.Assertions
+	require    *require.Assertions
+	f1         *f1.F1
+	errCh      chan error
+	scenario   string
+	logOutput  bytes.Buffer
+	runCount   atomic.Uint32
 }
 
 func newF1Stage(t *testing.T) (*f1Stage, *f1Stage, *f1Stage) {
@@ -46,6 +49,13 @@ func (s *f1Stage) and() *f1Stage {
 	return s
 }
 
+func (s *f1Stage) a_custom_logger_is_configured_with_attr(key, value string) *f1Stage {
+	logger := log.NewTestLogger(&s.logOutput).With(key, value)
+	s.f1 = f1.New().WithLogger(logger)
+
+	return s
+}
+
 func (s *f1Stage) after_duration_signal_will_be_sent(duration time.Duration, signal syscall.Signal) *f1Stage {
 	go func() {
 		time.Sleep(duration)
@@ -74,6 +84,20 @@ func (s *f1Stage) a_scenario_where_each_iteration_takes(duration time.Duration)
 	return s
 }
 
+func (s *f1Stage) a_scenario_that_logs() *f1Stage {
+	s.scenario = "logging_scenario"
+	s.f1.Add(s.scenario, func(sceanrioT *f1_testing.T) f1_testing.RunFn {
+		sceanrioT.Log("scenario")
+
+		return func(*f1_testing.T) {
+			sceanrioT.Log("iteration")
+			sceanrioT.Logger().Info("iteration")
+		}
+	})
+
+	return s
+}
+
 func (s *f1Stage) the_f1_scenario_is_executed_with_constant_rate_and_args(args ...string) *f1Stage {
 	err := s.f1.ExecuteWithArgs(append([]string{
 		"run", "constant", s.scenario,
@@ -115,3 +139,17 @@ func (s *f1Stage) expect_no_goroutines_to_run() *f1Stage {
 
 	return s
 }
+
+func (s *f1Stage) expect_all_log_lines_to_contain_attr(key, value string) *f1Stage {
+	lines := strings.Split(s.logOutput.String(), "\n")
+
+	s.require.Len(lines, 7)
+
+	for _, line := range lines {
+		if line != "" {
+			s.require.Contains(line, fmt.Sprintf(" %s=%s ", key, value))
+		}
+	}
+
+	return s
+}

pkg/f1/f1_test.go

@@ -45,3 +45,20 @@ func TestMissingScenario(t *testing.T) {
 	then.
 		the_execute_command_returns_an_error("scenario not defined: unknownScenario")
 }
+
+func TestWithCustomLogger(t *testing.T) {
+	given, when, then := newF1Stage(t)
+
+	given.
+		a_custom_logger_is_configured_with_attr("custom", "value").and().
+		a_scenario_that_logs()
+
+	when.
+		the_f1_scenario_is_executed_with_constant_rate_and_args(
+			"--rate", "1/1s",
+			"--max-duration", "2s",
+		)
+
+	then.
+		expect_all_log_lines_to_contain_attr("custom", "value")
+}