Allow custom logger to be used in Background

internal/log/log.go

@@ -8,6 +8,7 @@ package log
 import (
 	"io"
 	stdlog "log"
+	"os"
 )
 
 func NewLogger(out io.Writer) *Logger {
@@ -20,6 +21,11 @@ type Logger struct {
 	*stdlog.Logger
 }
 
+func (l *Logger) Debug(format string, args ...interface{}) {
+	format = "DEBUG: " + format
+	l.Printf(format, args...)
+}
+
 func (l *Logger) Info(format string, args ...interface{}) {
 	format = "INFO: " + format
 	l.Printf(format, args...)
@@ -34,3 +40,9 @@ func (l *Logger) Error(format string, args ...interface{}) {
 	format = "ERROR: " + format
 	l.Printf(format, args...)
 }
+
+func (l *Logger) Fatal(format string, args ...interface{}) {
+	format = "FATAL: " + format
+	l.Printf(format, args...)
+	os.Exit(1)
+}

internal/log/log_test.go

@@ -24,6 +24,38 @@ type tester struct {
 	wantPattern string // regexp that log output must match
 }
 
+func TestLoggerDebug(t *testing.T) {
+	tests := []tester{
+		{
+			desc:        "without trailing newline, logger adds newline",
+			message:     "hello, world!",
+			wantPattern: fmt.Sprintf("^%s %s%s DEBUG: hello, world!\n$", rgxdate, rgxtime, rgxmicroseconds),
+		},
+		{
+			desc:        "with trailing newline, logger preserves newline",
+			message:     "hello, world!\n",
+			wantPattern: fmt.Sprintf("^%s %s%s DEBUG: hello, world!\n$", rgxdate, rgxtime, rgxmicroseconds),
+		},
+	}
+
+	for _, tc := range tests {
+		var buf bytes.Buffer
+		logger := NewLogger(&buf)
+
+		logger.Debug(tc.message)
+
+		got := buf.String()
+		matched, err := regexp.MatchString(tc.wantPattern, got)
+		if err != nil {
+			t.Fatal("pattern did not compile:", err)
+		}
+		if !matched {
+			t.Errorf("logger.info(%q) outputted %q, should match pattern %q",
+				tc.message, got, tc.wantPattern)
+		}
+	}
+}
+
 func TestLoggerInfo(t *testing.T) {
 	tests := []tester{
 		{