cmd/devp2p, internal/utesting: implement TAP output (#21760)

TAP is a text format for test results. Parsers for it are available in many languages,
making it easy to consume. I want TAP output from our protocol tests because the
Hive wrapper around them needs to know about the test names and their individual
results and logs. It would also be possible to just write this info as JSON, but I don't
want to invent a new format.

This also improves the normal console output for tests (when running without --tap).
It now prints -- RUN lines before any output from the test, and indents the log output
by one space.

internal/utesting/utesting.go

@@ -25,6 +25,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"regexp"
 	"runtime"
 	"sync"
@@ -63,32 +64,165 @@ func MatchTests(tests []Test, expr string) []Test {
 // RunTests executes all given tests in order and returns their results.
 // If the report writer is non-nil, a test report is written to it in real time.
 func RunTests(tests []Test, report io.Writer) []Result {
-	results := make([]Result, len(tests))
+	if report == nil {
+		report = ioutil.Discard
+	}
+	results := run(tests, newConsoleOutput(report))
+	fails := CountFailures(results)
+	fmt.Fprintf(report, "%v/%v tests passed.\n", len(tests)-fails, len(tests))
+	return results
+}
+
+// RunTAP runs the given tests and writes Test Anything Protocol output
+// to the report writer.
+func RunTAP(tests []Test, report io.Writer) []Result {
+	return run(tests, newTAP(report, len(tests)))
+}
+
+func run(tests []Test, output testOutput) []Result {
+	var results = make([]Result, len(tests))
 	for i, test := range tests {
-		var output io.Writer
 		buffer := new(bytes.Buffer)
-		output = buffer
-		if report != nil {
-			output = io.MultiWriter(buffer, report)
-		}
+		logOutput := io.MultiWriter(buffer, output)
+
+		output.testStart(test.Name)
 		start := time.Now()
 		results[i].Name = test.Name
-		results[i].Failed = run(test, output)
+		results[i].Failed = runTest(test, logOutput)
 		results[i].Duration = time.Since(start)
 		results[i].Output = buffer.String()
-		if report != nil {
-			printResult(results[i], report)
-		}
+		output.testResult(results[i])
 	}
 	return results
 }
 
-func printResult(r Result, w io.Writer) {
+// testOutput is implemented by output formats.
+type testOutput interface {
+	testStart(name string)
+	Write([]byte) (int, error)
+	testResult(Result)
+}
+
+// consoleOutput prints test results similarly to go test.
+type consoleOutput struct {
+	out         io.Writer
+	indented    *indentWriter
+	curTest     string
+	wroteHeader bool
+}
+
+func newConsoleOutput(w io.Writer) *consoleOutput {
+	return &consoleOutput{
+		out:      w,
+		indented: newIndentWriter(" ", w),
+	}
+}
+
+// testStart signals the start of a new test.
+func (c *consoleOutput) testStart(name string) {
+	c.curTest = name
+	c.wroteHeader = false
+}
+
+// Write handles test log output.
+func (c *consoleOutput) Write(b []byte) (int, error) {
+	if !c.wroteHeader {
+		// This is the first output line from the test. Print a "-- RUN" header.
+		fmt.Fprintln(c.out, "-- RUN", c.curTest)
+		c.wroteHeader = true
+	}
+	return c.indented.Write(b)
+}
+
+// testResult prints the final test result line.
+func (c *consoleOutput) testResult(r Result) {
+	c.indented.flush()
 	pd := r.Duration.Truncate(100 * time.Microsecond)
 	if r.Failed {
-		fmt.Fprintf(w, "-- FAIL %s (%v)\n", r.Name, pd)
+		fmt.Fprintf(c.out, "-- FAIL %s (%v)\n", r.Name, pd)
 	} else {
-		fmt.Fprintf(w, "-- OK %s (%v)\n", r.Name, pd)
+		fmt.Fprintf(c.out, "-- OK %s (%v)\n", r.Name, pd)
+	}
+}
+
+// tapOutput produces Test Anything Protocol v13 output.
+type tapOutput struct {
+	out      io.Writer
+	indented *indentWriter
+	counter  int
+}
+
+func newTAP(out io.Writer, numTests int) *tapOutput {
+	fmt.Fprintf(out, "1..%d\n", numTests)
+	return &tapOutput{
+		out:      out,
+		indented: newIndentWriter("# ", out),
+	}
+}
+
+func (t *tapOutput) testStart(name string) {
+	t.counter++
+}
+
+// Write does nothing for TAP because there is no real-time output of test logs.
+func (t *tapOutput) Write(b []byte) (int, error) {
+	return len(b), nil
+}
+
+func (t *tapOutput) testResult(r Result) {
+	status := "ok"
+	if r.Failed {
+		status = "not ok"
+	}
+	fmt.Fprintln(t.out, status, t.counter, r.Name)
+	t.indented.Write([]byte(r.Output))
+	t.indented.flush()
+}
+
+// indentWriter indents all written text.
+type indentWriter struct {
+	out    io.Writer
+	indent string
+	inLine bool
+}
+
+func newIndentWriter(indent string, out io.Writer) *indentWriter {
+	return &indentWriter{out: out, indent: indent}
+}
+
+func (w *indentWriter) Write(b []byte) (n int, err error) {
+	for len(b) > 0 {
+		if !w.inLine {
+			if _, err = io.WriteString(w.out, w.indent); err != nil {
+				return n, err
+			}
+			w.inLine = true
+		}
+
+		end := bytes.IndexByte(b, '\n')
+		if end == -1 {
+			nn, err := w.out.Write(b)
+			n += nn
+			return n, err
+		}
+
+		line := b[:end+1]
+		nn, err := w.out.Write(line)
+		n += nn
+		if err != nil {
+			return n, err
+		}
+		b = b[end+1:]
+		w.inLine = false
+	}
+	return n, err
+}
+
+// flush ensures the current line is terminated.
+func (w *indentWriter) flush() {
+	if w.inLine {
+		fmt.Println(w.out)
+		w.inLine = false
 	}
 }
 
@@ -106,11 +240,11 @@ func CountFailures(rr []Result) int {
 // Run executes a single test.
 func Run(test Test) (bool, string) {
 	output := new(bytes.Buffer)
-	failed := run(test, output)
+	failed := runTest(test, output)
 	return failed, output.String()
 }
 
-func run(test Test, output io.Writer) bool {
+func runTest(test Test, output io.Writer) bool {
 	t := &T{output: output}
 	done := make(chan struct{})
 	go func() {
@@ -137,6 +271,9 @@ type T struct {
 	output io.Writer
 }
 
+// Helper exists for compatibility with testing.T.
+func (t *T) Helper() {}
+
 // FailNow marks the test as having failed and stops its execution by calling
 // runtime.Goexit (which then runs all deferred calls in the current goroutine).
 func (t *T) FailNow() {