assert: collect.FailNow() should not panic

Fixes stretchr#1396
Fixes stretchr#1457

assert/assertions.go

@@ -1860,20 +1860,24 @@ func Eventually(t TestingT, condition func() bool, waitFor time.Duration, tick t
 // CollectT implements the TestingT interface and collects all errors.
 type CollectT struct {
 	errors []error
+	failed bool
 }
 
 // Errorf collects the error.
 func (c *CollectT) Errorf(format string, args ...interface{}) {
+	c.failed = true
 	c.errors = append(c.errors, fmt.Errorf(format, args...))
 }
 
 // FailNow panics.
 func (c *CollectT) FailNow() {
-	panic("Assertion failed")
+	c.failed = true
+	runtime.Goexit()
 }
 
 // Reset clears the collected errors.
 func (c *CollectT) Reset() {
+	c.failed = false
 	c.errors = nil
 }
 
@@ -1928,8 +1932,8 @@ func EventuallyWithT(t TestingT, condition func(collect *CollectT), waitFor time
 			tick = nil
 			collect.Reset()
 			go func() {
+				defer func() { ch <- !collect.failed }()
 				condition(collect)
-				ch <- len(collect.errors) == 0
 			}()
 		case v := <-ch:
 			if v {

assert/assertions_test.go

@@ -2786,6 +2786,17 @@ func TestEventuallyWithTTrue(t *testing.T) {
 	Len(t, mockT.errors, 0)
 }
 
+func TestEventuallyWithTFailNow(t *testing.T) {
+	mockT := new(CollectT)
+
+	condition := func(collect *CollectT) {
+		collect.FailNow()
+	}
+
+	False(t, EventuallyWithT(mockT, condition, 100*time.Millisecond, 20*time.Millisecond))
+	Len(t, mockT.errors, 1)
+}
+
 func TestNeverFalse(t *testing.T) {
 	condition := func() bool {
 		return false

require/requirements_test.go

@@ -5,6 +5,8 @@ import (
 	"errors"
 	"testing"
 	"time"
+
+	"github.com/stretchr/testify/assert"
 )
 
 // AssertionTesterInterface defines an interface to be used for testing assertion methods
@@ -681,3 +683,33 @@ func TestErrorAssertionFunc(t *testing.T) {
 		})
 	}
 }
+
+func TestEventuallyWithTFalse(t *testing.T) {
+	mockT := new(MockT)
+
+	condition := func(collect *assert.CollectT) {
+		True(collect, false)
+	}
+
+	EventuallyWithT(mockT, condition, 100*time.Millisecond, 20*time.Millisecond)
+	if !mockT.Failed {
+		t.Error("Check should fail")
+	}
+}
+
+func TestEventuallyWithTTrue(t *testing.T) {
+	mockT := new(MockT)
+
+	state := 0
+	condition := func(collect *assert.CollectT) {
+		defer func() {
+			state += 1
+		}()
+		True(collect, state == 2)
+	}
+
+	EventuallyWithT(mockT, condition, 100*time.Millisecond, 20*time.Millisecond)
+	if mockT.Failed {
+		t.Error("Check should pass")
+	}
+}