Add Never assertion

Never asserts that a conditon isn't met within a given timeframe.

assert/assertion_format.go

@@ -363,6 +363,17 @@ func LessOrEqualf(t TestingT, e1 interface{}, e2 interface{}, msg string, args .
 	return LessOrEqual(t, e1, e2, append([]interface{}{msg}, args...)...)
 }
 
+// Neverf asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    assert.Neverf(t, func() bool { return false; }, time.Second, 10*time.Millisecond, "error message %s", "formatted")
+func Neverf(t TestingT, condition func() bool, waitFor time.Duration, tick time.Duration, msg string, args ...interface{}) bool {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	return Never(t, condition, waitFor, tick, append([]interface{}{msg}, args...)...)
+}
+
 // Nilf asserts that the specified object is nil.
 //
 //    assert.Nilf(t, err, "error message %s", "formatted")

assert/assertion_forward.go

@@ -715,6 +715,28 @@ func (a *Assertions) Lessf(e1 interface{}, e2 interface{}, msg string, args ...i
 	return Lessf(a.t, e1, e2, msg, args...)
 }
 
+// Never asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    a.Never(func() bool { return false; }, time.Second, 10*time.Millisecond)
+func (a *Assertions) Never(condition func() bool, waitFor time.Duration, tick time.Duration, msgAndArgs ...interface{}) bool {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	return Never(a.t, condition, waitFor, tick, msgAndArgs...)
+}
+
+// Neverf asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    a.Neverf(func() bool { return false; }, time.Second, 10*time.Millisecond, "error message %s", "formatted")
+func (a *Assertions) Neverf(condition func() bool, waitFor time.Duration, tick time.Duration, msg string, args ...interface{}) bool {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	return Neverf(a.t, condition, waitFor, tick, msg, args...)
+}
+
 // Nil asserts that the specified object is nil.
 //
 //    a.Nil(err)

assert/assertions.go

@@ -1591,3 +1591,36 @@ func Eventually(t TestingT, condition func() bool, waitFor time.Duration, tick t
 		}
 	}
 }
+
+// Never asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    assert.Never(t, func() bool { return false; }, time.Second, 10*time.Millisecond)
+func Never(t TestingT, condition func() bool, waitFor time.Duration, tick time.Duration, msgAndArgs ...interface{}) bool {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+
+	ch := make(chan bool, 1)
+
+	timer := time.NewTimer(waitFor)
+	defer timer.Stop()
+
+	ticker := time.NewTicker(tick)
+	defer ticker.Stop()
+
+	for tick := ticker.C; ; {
+		select {
+		case <-timer.C:
+			return true
+		case <-tick:
+			tick = nil
+			go func() { ch <- condition() }()
+		case v := <-ch:
+			if v {
+				return Fail(t, "Condition satisfied", msgAndArgs...)
+			}
+			tick = ticker.C
+		}
+	}
+}

assert/assertions_test.go

@@ -2167,6 +2167,27 @@ func TestEventuallyTrue(t *testing.T) {
 	True(t, Eventually(t, condition, 100*time.Millisecond, 20*time.Millisecond))
 }
 
+func TestNeverFalse(t *testing.T) {
+	condition := func() bool {
+		return false
+	}
+
+	True(t, Never(t, condition, 100*time.Millisecond, 20*time.Millisecond))
+}
+
+func TestNeverTrue(t *testing.T) {
+	mockT := new(testing.T)
+	state := 0
+	condition := func() bool {
+		defer func() {
+			state = state + 1
+		}()
+		return state == 2
+	}
+
+	False(t, Never(mockT, condition, 100*time.Millisecond, 20*time.Millisecond))
+}
+
 func TestEventuallyIssue805(t *testing.T) {
 	mockT := new(testing.T)
 

require/require.go

@@ -914,6 +914,34 @@ func Lessf(t TestingT, e1 interface{}, e2 interface{}, msg string, args ...inter
 	t.FailNow()
 }
 
+// Never asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    assert.Never(t, func() bool { return false; }, time.Second, 10*time.Millisecond)
+func Never(t TestingT, condition func() bool, waitFor time.Duration, tick time.Duration, msgAndArgs ...interface{}) {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	if assert.Never(t, condition, waitFor, tick, msgAndArgs...) {
+		return
+	}
+	t.FailNow()
+}
+
+// Neverf asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    assert.Neverf(t, func() bool { return false; }, time.Second, 10*time.Millisecond, "error message %s", "formatted")
+func Neverf(t TestingT, condition func() bool, waitFor time.Duration, tick time.Duration, msg string, args ...interface{}) {
+	if h, ok := t.(tHelper); ok {
+		h.Helper()
+	}
+	if assert.Neverf(t, condition, waitFor, tick, msg, args...) {
+		return
+	}
+	t.FailNow()
+}
+
 // Nil asserts that the specified object is nil.
 //
 //    assert.Nil(t, err)

require/require_forward.go

@@ -716,6 +716,28 @@ func (a *Assertions) Lessf(e1 interface{}, e2 interface{}, msg string, args ...i
 	Lessf(a.t, e1, e2, msg, args...)
 }
 
+// Never asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    a.Never(func() bool { return false; }, time.Second, 10*time.Millisecond)
+func (a *Assertions) Never(condition func() bool, waitFor time.Duration, tick time.Duration, msgAndArgs ...interface{}) {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	Never(a.t, condition, waitFor, tick, msgAndArgs...)
+}
+
+// Neverf asserts that the given condition doesn't satisfy in waitFor time,
+// periodically checking the target function each tick.
+//
+//    a.Neverf(func() bool { return false; }, time.Second, 10*time.Millisecond, "error message %s", "formatted")
+func (a *Assertions) Neverf(condition func() bool, waitFor time.Duration, tick time.Duration, msg string, args ...interface{}) {
+	if h, ok := a.t.(tHelper); ok {
+		h.Helper()
+	}
+	Neverf(a.t, condition, waitFor, tick, msg, args...)
+}
+
 // Nil asserts that the specified object is nil.
 //
 //    a.Nil(err)