better tests

go.mod

@@ -2,7 +2,10 @@ module github.com/FollowTheProcess/log
 
 go 1.24
 
-require github.com/FollowTheProcess/hue v0.5.2
+require (
+	github.com/FollowTheProcess/hue v0.5.2
+	github.com/FollowTheProcess/test v0.21.0
+)
 
 require (
 	golang.org/x/sys v0.31.0 // indirect

go.sum

@@ -1,6 +1,12 @@
 github.com/FollowTheProcess/hue v0.5.2 h1:Ns/vO8wiwv2oXDn+QyBLcYCK0LcfXVVu31bHGTLAFHI=
 github.com/FollowTheProcess/hue v0.5.2/go.mod h1:5FD2UrxTzWi0Uc63w8ndsjqPrH4xn3Q7k7vEpINqEP4=
+github.com/FollowTheProcess/snapshot v0.4.1 h1:WIwvs+yZrK9886frLbNB98QWkAXTjIGnuvEjURHOrtE=
+github.com/FollowTheProcess/snapshot v0.4.1/go.mod h1:hb3V3azvp8FVrl4pvyhvq/ZYOnFSgyKHfXt96Jgg4e0=
+github.com/FollowTheProcess/test v0.21.0 h1:8eljlAhdOusGXgEso8It6ymvk+Ua3MenNH3+4jp0+dY=
+github.com/FollowTheProcess/test v0.21.0/go.mod h1:3UQ3s3EsAuD9Hw5aekXIxssqhIx7kCTjw2lKtYb0uFo=
 golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
 golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 golang.org/x/term v0.30.0 h1:PQ39fJZ+mfadBm0y5WlL4vlM7Sx1Hgf13sMIY2+QS9Y=
 golang.org/x/term v0.30.0/go.mod h1:NYYFdzHoI5wRh/h5tDMdMqCqPJZEuNqVR5xJLd/n67g=
+golang.org/x/tools v0.31.0 h1:0EedkvKDbh+qistFTd0Bcwe/YLh4vHwWEkiI0toFIBU=
+golang.org/x/tools v0.31.0/go.mod h1:naFTU+Cev749tSJRXJlna0T3WxKvb1kWEx15xA4SdmQ=

log_test.go

@@ -5,15 +5,19 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"strings"
 	"sync"
 	"testing"
+	"time"
 
 	"github.com/FollowTheProcess/hue"
 	"github.com/FollowTheProcess/log"
+	"github.com/FollowTheProcess/test"
 )
 
 func TestVisual(t *testing.T) {
 	hue.Enabled(true) // Force colour
+
 	logger := log.New(os.Stdout, log.WithLevel(log.LevelDebug))
 
 	logger.Debug("Doing some debuggy things")
@@ -22,27 +26,97 @@ func TestVisual(t *testing.T) {
 	logger.Error("File not found")
 }
 
+func TestDebug(t *testing.T) {
+	hue.Enabled(false) // Force no color
+
+	// Constantly return the same time
+	fixedTime := func() time.Time {
+		fixed, err := time.Parse(time.RFC3339, "2025-04-01T13:34:03Z")
+		test.Ok(t, err)
+
+		return fixed
+	}
+
+	fixedTimeString := fixedTime().Format(time.RFC3339)
+
+	tests := []struct {
+		name    string
+		msg     string
+		want    string
+		options []log.Option
+	}{
+		{
+			name: "disabled",
+			options: []log.Option{
+				log.WithLevel(log.LevelInfo),
+			},
+			msg:  "You should not see me",
+			want: "", // Debug logs should not show up if the level is info
+		},
+		{
+			name: "enabled",
+			options: []log.Option{
+				log.WithLevel(log.LevelDebug),
+			},
+			msg:  "Hello debug!",
+			want: "[TIME] DEBUG: Hello debug!\n",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			buf := &bytes.Buffer{}
+
+			// Ensure that the time is always deterministic
+			tt.options = append(tt.options, log.TimeFunc(fixedTime))
+
+			logger := log.New(buf, tt.options...)
+
+			logger.Debug(tt.msg)
+
+			got := buf.String()
+			got = strings.ReplaceAll(got, fixedTimeString, "[TIME]")
+
+			test.Diff(t, got, tt.want)
+		})
+	}
+}
+
 func TestRace(t *testing.T) {
 	buf := &bytes.Buffer{}
-	logger := log.New(buf)
+
+	// Constantly return the same time
+	fixedTime := func() time.Time {
+		fixed, err := time.Parse(time.RFC3339, "2025-04-01T13:34:03Z")
+		test.Ok(t, err)
+
+		return fixed
+	}
+
+	logger := log.New(buf, log.TimeFunc(fixedTime))
 
 	const n = 5
 
 	var wg sync.WaitGroup
 	wg.Add(n)
-	for range n {
-		go func(wg *sync.WaitGroup) {
+	for i := range n {
+		go func(wg *sync.WaitGroup, i int) {
 			defer wg.Done()
-			logger.Info(fmt.Sprintf("Something: %d", n))
-		}(&wg)
+			logger.Info(fmt.Sprintf("Something: %d", i))
+		}(&wg, i)
 	}
 
 	wg.Wait()
+
+	// Make sure they all got written, order doesn't matter because concurrency
+	got := strings.TrimSpace(buf.String())
+	lines := strings.Split(got, "\n")
+
+	test.Equal(t, len(lines), n, test.Context("expected %d log lines", n))
 }
 
 func BenchmarkLogger(b *testing.B) {
 	hue.Enabled(true) // Force colour
-	defer hue.Enabled(false)
 
 	b.Run("enabled", func(b *testing.B) {
 		buf := &bytes.Buffer{}