test(all): add Retry func to testutil from samples repository (#4902)

* test(all): add retry functions to testutil

Author: crwilcox

internal/testutil/retry.go

@@ -0,0 +1,116 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testutil
+
+import (
+	"bytes"
+	"fmt"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"testing"
+	"time"
+)
+
+// Retry runs function f for up to maxAttempts times until f returns successfully, and reports whether f was run successfully.
+// It will sleep for the given period between invocations of f.
+// Use the provided *testutil.R instead of a *testing.T from the function.
+func Retry(t *testing.T, maxAttempts int, sleep time.Duration, f func(r *R)) bool {
+	for attempt := 1; attempt <= maxAttempts; attempt++ {
+		r := &R{Attempt: attempt, log: &bytes.Buffer{}}
+
+		f(r)
+
+		if !r.failed {
+			if r.log.Len() != 0 {
+				t.Logf("Success after %d attempts:%s", attempt, r.log.String())
+			}
+			return true
+		}
+
+		if attempt == maxAttempts {
+			t.Logf("FAILED after %d attempts:%s", attempt, r.log.String())
+			t.Fail()
+		}
+
+		time.Sleep(sleep)
+	}
+	return false
+}
+
+// RetryWithoutTest is a variant of Retry that does not use a testing parameter.
+// It is meant for testing utilities that do not pass around the testing context, such as cloudrunci.
+func RetryWithoutTest(maxAttempts int, sleep time.Duration, f func(r *R)) bool {
+	for attempt := 1; attempt <= maxAttempts; attempt++ {
+		r := &R{Attempt: attempt, log: &bytes.Buffer{}}
+
+		f(r)
+
+		if !r.failed {
+			if r.log.Len() != 0 {
+				r.Logf("Success after %d attempts:%s", attempt, r.log.String())
+			}
+			return true
+		}
+
+		if attempt == maxAttempts {
+			r.Logf("FAILED after %d attempts:%s", attempt, r.log.String())
+			return false
+		}
+
+		time.Sleep(sleep)
+	}
+	return false
+}
+
+// R is passed to each run of a flaky test run, manages state and accumulates log statements.
+type R struct {
+	// The number of current attempt.
+	Attempt int
+
+	failed bool
+	log    *bytes.Buffer
+}
+
+// Fail marks the run as failed, and will retry once the function returns.
+func (r *R) Fail() {
+	r.failed = true
+}
+
+// Errorf is equivalent to Logf followed by Fail.
+func (r *R) Errorf(s string, v ...interface{}) {
+	r.logf(s, v...)
+	r.Fail()
+}
+
+// Logf formats its arguments and records it in the error log.
+// The text is only printed for the final unsuccessful run or the first successful run.
+func (r *R) Logf(s string, v ...interface{}) {
+	r.logf(s, v...)
+}
+
+func (r *R) logf(s string, v ...interface{}) {
+	fmt.Fprint(r.log, "\n")
+	fmt.Fprint(r.log, lineNumber())
+	fmt.Fprintf(r.log, s, v...)
+}
+
+func lineNumber() string {
+	_, file, line, ok := runtime.Caller(3) // logf, public func, user function
+	if !ok {
+		return ""
+	}
+	return filepath.Base(file) + ":" + strconv.Itoa(line) + ": "
+}

internal/testutil/retry_test.go

@@ -0,0 +1,76 @@
+// Copyright 2019 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package testutil
+
+import (
+	"testing"
+	"time"
+)
+
+func TestRetry(t *testing.T) {
+	Retry(t, 5, time.Millisecond, func(r *R) {
+		if r.Attempt == 2 {
+			return
+		}
+		r.Fail()
+	})
+}
+
+func TestRetryAttempts(t *testing.T) {
+	var attempts int
+	Retry(t, 10, time.Millisecond, func(r *R) {
+		r.Logf("This line should appear only once.")
+		r.Logf("attempt=%d", r.Attempt)
+		attempts = r.Attempt
+
+		// Retry 5 times.
+		if r.Attempt == 5 {
+			return
+		}
+		r.Fail()
+	})
+
+	if attempts != 5 {
+		t.Errorf("attempts=%d; want %d", attempts, 5)
+	}
+}
+
+func TestRetryWithoutTest(t *testing.T) {
+	RetryWithoutTest(5, time.Millisecond, func(r *R) {
+		if r.Attempt == 2 {
+			return
+		}
+		r.Fail()
+	})
+}
+
+func TestRetryWithoutTestAttempts(t *testing.T) {
+	var attempts int
+	RetryWithoutTest(10, time.Millisecond, func(r *R) {
+		r.Logf("This line should appear only once.")
+		r.Logf("attempt=%d", r.Attempt)
+		attempts = r.Attempt
+
+		// Retry 5 times.
+		if r.Attempt == 5 {
+			return
+		}
+		r.Fail()
+	})
+
+	if attempts != 5 {
+		t.Errorf("attempts=%d; want %d", attempts, 5)
+	}
+}