assert: check early in Eventually, EventuallyWithT, and Never

assert/assertions.go

@@ -1931,25 +1931,31 @@ func Eventually(t TestingT, condition func() bool, waitFor time.Duration, tick t
 	}
 
 	ch := make(chan bool, 1)
+	checkCond := func() { ch <- condition() }
 
 	timer := time.NewTimer(waitFor)
 	defer timer.Stop()
 
 	ticker := time.NewTicker(tick)
 	defer ticker.Stop()
 
-	for tick := ticker.C; ; {
+	var tickC <-chan time.Time
+
+	// Check the condition once first on the initial call.
+	go checkCond()
+
+	for {
 		select {
 		case <-timer.C:
 			return Fail(t, "Condition never satisfied", msgAndArgs...)
-		case <-tick:
-			tick = nil
-			go func() { ch <- condition() }()
+		case <-tickC:
+			tickC = nil
+			go checkCond()
 		case v := <-ch:
 			if v {
 				return true
 			}
-			tick = ticker.C
+			tickC = ticker.C
 		}
 	}
 }
@@ -2005,35 +2011,42 @@ func EventuallyWithT(t TestingT, condition func(collect *CollectT), waitFor time
 	var lastFinishedTickErrs []error
 	ch := make(chan []error, 1)
 
+	checkCond := func() {
+		collect := new(CollectT)
+		defer func() {
+			ch <- collect.errors
+		}()
+		condition(collect)
+	}
+
 	timer := time.NewTimer(waitFor)
 	defer timer.Stop()
 
 	ticker := time.NewTicker(tick)
 	defer ticker.Stop()
 
-	for tick := ticker.C; ; {
+	var tickC <-chan time.Time
+
+	// Check the condition once first on the initial call.
+	go checkCond()
+
+	for {
 		select {
 		case <-timer.C:
 			for _, err := range lastFinishedTickErrs {
 				t.Errorf("%v", err)
 			}
 			return Fail(t, "Condition never satisfied", msgAndArgs...)
-		case <-tick:
-			tick = nil
-			go func() {
-				collect := new(CollectT)
-				defer func() {
-					ch <- collect.errors
-				}()
-				condition(collect)
-			}()
+		case <-tickC:
+			tickC = nil
+			go checkCond()
 		case errs := <-ch:
 			if len(errs) == 0 {
 				return true
 			}
 			// Keep the errors from the last ended condition, so that they can be copied to t if timeout is reached.
 			lastFinishedTickErrs = errs
-			tick = ticker.C
+			tickC = ticker.C
 		}
 	}
 }
@@ -2048,25 +2061,31 @@ func Never(t TestingT, condition func() bool, waitFor time.Duration, tick time.D
 	}
 
 	ch := make(chan bool, 1)
+	checkCond := func() { ch <- condition() }
 
 	timer := time.NewTimer(waitFor)
 	defer timer.Stop()
 
 	ticker := time.NewTicker(tick)
 	defer ticker.Stop()
 
-	for tick := ticker.C; ; {
+	var tickC <-chan time.Time
+
+	// Check the condition once first on the initial call.
+	go checkCond()
+
+	for {
 		select {
 		case <-timer.C:
 			return true
-		case <-tick:
-			tick = nil
-			go func() { ch <- condition() }()
+		case <-tickC:
+			tickC = nil
+			go checkCond()
 		case v := <-ch:
 			if v {
 				return Fail(t, "Condition satisfied", msgAndArgs...)
 			}
-			tick = ticker.C
+			tickC = ticker.C
 		}
 	}
 }

assert/assertions_test.go

@@ -2970,6 +2970,49 @@ func TestEventuallyWithT_ReturnsTheLatestFinishedConditionErrors(t *testing.T) {
 	Len(t, mockT.errors, 2)
 }
 
+// Check that a long running condition doesn't block Eventually.
+// See issue 805 (and its long tail of following issues)
+func TestEventuallyTimeout(t *testing.T) {
+	mockT := new(testing.T)
+
+	NotPanics(t, func() {
+		done, done2 := make(chan struct{}), make(chan struct{})
+
+		// A condition function that returns after the Eventually timeout
+		condition := func() bool {
+			// Wait until Eventually times out and terminates
+			<-done
+			close(done2)
+			return true
+		}
+
+		False(t, Eventually(mockT, condition, time.Millisecond, time.Microsecond))
+
+		close(done)
+		<-done2
+	})
+}
+
+func TestEventuallySucceedQuickly(t *testing.T) {
+	mockT := new(testing.T)
+
+	condition := func() bool { return true }
+
+	// By making the tick longer than the total duration, we expect that this test would fail if
+	// we didn't check the condition before the first tick elapses.
+	True(t, Eventually(mockT, condition, 100*time.Millisecond, time.Second))
+}
+
+func TestEventuallyWithTSucceedQuickly(t *testing.T) {
+	mockT := new(testing.T)
+
+	condition := func(t *CollectT) {}
+
+	// By making the tick longer than the total duration, we expect that this test would fail if
+	// we didn't check the condition before the first tick elapses.
+	True(t, EventuallyWithT(mockT, condition, 100*time.Millisecond, time.Second))
+}
+
 func TestNeverFalse(t *testing.T) {
 	condition := func() bool {
 		return false
@@ -2997,27 +3040,13 @@ func TestNeverTrue(t *testing.T) {
 	False(t, Never(mockT, condition, 100*time.Millisecond, 20*time.Millisecond))
 }
 
-// Check that a long running condition doesn't block Eventually.
-// See issue 805 (and its long tail of following issues)
-func TestEventuallyTimeout(t *testing.T) {
+func TestNeverFailQuickly(t *testing.T) {
 	mockT := new(testing.T)
 
-	NotPanics(t, func() {
-		done, done2 := make(chan struct{}), make(chan struct{})
-
-		// A condition function that returns after the Eventually timeout
-		condition := func() bool {
-			// Wait until Eventually times out and terminates
-			<-done
-			close(done2)
-			return true
-		}
-
-		False(t, Eventually(mockT, condition, time.Millisecond, time.Microsecond))
-
-		close(done)
-		<-done2
-	})
+	// By making the tick longer than the total duration, we expect that this test would fail if
+	// we didn't check the condition before the first tick elapses.
+	condition := func() bool { return true }
+	False(t, Never(mockT, condition, 100*time.Millisecond, time.Second))
 }
 
 func Test_validateEqualArgs(t *testing.T) {