add t.Output

Author: mxey

engine.go

@@ -12,6 +12,7 @@ import (
 	"encoding/binary"
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"os"
 	"path/filepath"
@@ -778,6 +779,39 @@ func (t *T) Log(args ...any) {
 	}
 }
 
+// Output returns a Writer that writes to the same test output stream as T.Log.
+// The output is indented like T.Log lines, but Output does not
+// add source locations or newlines. The output is internally line
+// buffered, and a call to T.Log or the end of the test will implicitly
+// flush the buffer, followed by a newline. After a test function and all its
+// parents return, neither Output nor the Write method may be called.
+//
+// If running on Go <= 1.25, where testing's t.Output is not available,
+// it falls back to using t.Log.
+func (t *T) Output() io.Writer {
+	if t.rawLog != nil {
+		return t.rawLog.Writer()
+	} else if t.tbLog {
+		if tout, ok := t.tb.(interface{ Output() io.Writer }); ok {
+			return tout.Output()
+		} else {
+			return &tbWriter{t.tb}
+		}
+	} else {
+		return io.Discard
+	}
+}
+
+type tbWriter struct {
+	tb
+}
+
+func (w *tbWriter) Write(b []byte) (int, error) {
+	w.tb.Helper()
+	w.tb.Logf("%s", b)
+	return len(b), nil
+}
+
 // Skipf is equivalent to [T.Logf] followed by [T.SkipNow].
 func (t *T) Skipf(format string, args ...any) {
 	if t.tbLog {