Fixes

lectures/04-testing/lecture.slide

@@ -241,6 +241,11 @@ Good example
 
 * testify
 
+  import (
+      "testing"
+      "github.com/stretchr/testify/assert"
+  )
+
   func TestSum0(t *testing.T) {
       assert.Equalf(t, 4, Sum(1, 2), "Sum(%d, %d)", 1, 2)
   }
@@ -334,7 +339,7 @@ Good example
       // false
   }
 
-Если `Output` нет, то `Example` слушит только для документации.
+Если `Output` нет, то `Example` служит только для документации.
 
   func ExampleAPI() {
       var c *Client // skip initialization
@@ -378,6 +383,7 @@ Good example
 * t.Helper()
 
   func assertGood(t *testing.T, i int) {
+      t.Helper()
       if i != 0 {
           t.Errorf("i (= %d) != 0", i)
       }
@@ -446,3 +452,38 @@ Good example
       }
   }
 
+* Race detector
+
+.play race/race_test.go
+
+* Race detector
+
+  prime@bee ~/C/shad-go> go test -race ./lectures/04-testing/race
+  ==================
+  WARNING: DATA RACE
+  Read at 0x00c000092090 by goroutine 8:
+    gitlab.com/slon/shad-go/lectures/04-testing/race.TestRace()
+        /home/prime/Code/shad-go/lectures/04-testing/race/race_test.go:25 +0x144
+    testing.tRunner()
+        /usr/local/go/src/testing/testing.go:909 +0x199
+
+  Previous write at 0x00c000092090 by goroutine 9:
+    gitlab.com/slon/shad-go/lectures/04-testing/race.TestRace.func1()
+        /home/prime/Code/shad-go/lectures/04-testing/race/race_test.go:17 +0x6c
+
+  ...
+  ==================
+  --- FAIL: TestRace (0.00s)
+      testing.go:853: race detected during execution of test
+  FAIL
+  FAIL	gitlab.com/slon/shad-go/lectures/04-testing/race	0.007s
+
+* White box testing
+
+.play mocks/mocks.go /var/,/OMIT/
+
+* White box testing
+
+.play mocks/mocks_test.go /func/,/^}/
+
+

lectures/04-testing/mocks/mocks.go

@@ -0,0 +1,29 @@
+import (
+	"fmt"
+	"log"
+	"net/smtp"
+)
+
+var notifyUser = doNotifyUser
+
+func doNotifyUser(username, msg string) {
+	auth := smtp.PlainAuth("", sender, password, hostname)
+	err := smtp.SendMail(hostname+":587", auth, sender,
+		[]string{username}, []byte(msg))
+	if err != nil {
+		log.Printf("smtp.SendEmail(%s) failed: %s", username, err)
+	}
+}
+
+func CheckQuota(username string) {
+	used := bytesInUse(username)
+	const quota = 1000000000 // 1GB
+	percent := 100 * used / quota
+	if percent < 90 {
+		return // OK
+	}
+	msg := fmt.Sprintf(template, used, percent)
+	notifyUser(username, msg)
+}
+
+// OMIT

lectures/04-testing/mocks/mocks_test.go

@@ -0,0 +1,26 @@
+import (
+	"strings"
+	"testing"
+)
+
+func TestCheckQuotaNotifiesUser(t *testing.T) {
+	var notifiedUser, notifiedMsg string
+	notifyUser = func(user, msg string) {
+		notifiedUser, notifiedMsg = user, msg
+	}
+	// ...simulate a 980MB-used condition...
+	const user = "joe@example.org"
+	CheckQuota(user)
+	if notifiedUser == "" && notifiedMsg == "" {
+		t.Fatalf("notifyUser not called")
+	}
+	if notifiedUser != user {
+		t.Errorf("wrong user (%s) notified, want %s",
+			notifiedUser, user)
+	}
+	const wantSubstring = "98% of your quota"
+	if !strings.Contains(notifiedMsg, wantSubstring) {
+		t.Errorf("unexpected notification message <<%s>>, "+
+			"want substring %q", notifiedMsg, wantSubstring)
+	}
+}

lectures/04-testing/race/race_test.go

@@ -0,0 +1,23 @@
+package race
+
+import (
+	"sync"
+	"testing"
+)
+
+func TestRace(t *testing.T) {
+	var wg sync.WaitGroup
+	defer wg.Wait()
+	wg.Add(2)
+
+	var i int
+	go func() {
+		defer wg.Done()
+		i = 0
+	}()
+	go func() {
+		defer wg.Done()
+		i = 1
+	}()
+	_ = i
+}