testing: add Output

api/next/59928.txt

@@ -0,0 +1,3 @@
+pkg testing, method (*B) Output() io.Writer #59928
+pkg testing, method (*F) Output() io.Writer #59928
+pkg testing, method (*T) Output() io.Writer #59928

doc/next/6-stdlib/99-minor/testing/59928.md

@@ -0,0 +1,4 @@
+<!-- go.dev/issue/59928 -->
+
+The new [Output] method of [testing.T], [testing.B] and [testing.F] provides a Writer
+that writes to the same test output stream as [TB.Log], but omits the file and line number.

src/testing/benchmark.go

@@ -755,6 +755,7 @@ func (s *benchState) processBench(b *B) {
 					benchFunc: b.benchFunc,
 					benchTime: b.benchTime,
 				}
+				b.setOutputWriter()
 				b.run1()
 			}
 			r := b.doBench()
@@ -831,6 +832,7 @@ func (b *B) Run(name string, f func(b *B)) bool {
 		benchTime:  b.benchTime,
 		bstate:     b.bstate,
 	}
+	sub.setOutputWriter()
 	if partial {
 		// Partial name match, like -bench=X/Y matching BenchmarkX.
 		// Only process sub-benchmarks, if any.
@@ -1007,6 +1009,7 @@ func Benchmark(f func(b *B)) BenchmarkResult {
 		benchFunc: f,
 		benchTime: benchTime,
 	}
+	b.setOutputWriter()
 	if b.run1() {
 		b.run()
 	}

src/testing/fuzz.go

@@ -320,6 +320,7 @@ func (f *F) Fuzz(ff any) {
 			t.parent.w = captureOut
 		}
 		t.w = indenter{&t.common}
+		t.setOutputWriter()
 		if t.chatty != nil {
 			t.chatty.Updatef(t.name, "=== RUN   %s\n", t.name)
 		}
@@ -529,6 +530,7 @@ func runFuzzTests(deps testDeps, fuzzTests []InternalFuzzTarget, deadline time.T
 					fstate: fstate,
 				}
 				f.w = indenter{&f.common}
+				f.setOutputWriter()
 				if f.chatty != nil {
 					f.chatty.Updatef(f.name, "=== RUN   %s\n", f.name)
 				}

src/testing/panic_test.go

@@ -34,15 +34,18 @@ func TestPanic(t *testing.T) {
 		want: `
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
 `,
 	}, {
 		desc:  "subtest panics",
 		flags: []string{"-test_panic_test=TestPanicHelper/1"},
 		want: `
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "subtest panics with cleanup",
@@ -53,8 +56,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "subtest panics with outer cleanup panic",
@@ -65,6 +70,7 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
 `,
 	}, {
 		desc:  "subtest panics with middle cleanup panic",
@@ -75,8 +81,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "subtest panics with inner cleanup panic",
@@ -87,8 +95,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "parallel subtest panics with cleanup",
@@ -99,8 +109,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "parallel subtest panics with outer cleanup panic",
@@ -111,6 +123,7 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
 `,
 	}, {
 		desc:  "parallel subtest panics with middle cleanup panic",
@@ -121,8 +134,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}, {
 		desc:  "parallel subtest panics with inner cleanup panic",
@@ -133,8 +148,10 @@ ran middle cleanup 1
 ran outer cleanup
 --- FAIL: TestPanicHelper (N.NNs)
     panic_test.go:NNN: TestPanicHelper
+    TestPanicHelper
     --- FAIL: TestPanicHelper/1 (N.NNs)
         panic_test.go:NNN: TestPanicHelper/1
+        TestPanicHelper/1
 `,
 	}}
 	for _, tc := range testCases {
@@ -165,6 +182,7 @@ func TestPanicHelper(t *testing.T) {
 		return
 	}
 	t.Log(t.Name())
+	t.Output().Write([]byte(t.Name()))
 	if t.Name() == *testPanicTest {
 		panic("panic")
 	}
@@ -195,6 +213,7 @@ func TestPanicHelper(t *testing.T) {
 				t.Parallel()
 			}
 			t.Log(t.Name())
+			t.Output().Write([]byte(t.Name()))
 			if chosen {
 				if *testPanicCleanup {
 					t.Cleanup(func() {