Added ShouldPanic

is.go

@@ -229,6 +229,18 @@ func (is *Is) Len(o interface{}, l int) {
 	}
 }
 
+// ShouldPanic expects the provided function to panic. If the function does
+// not panic, this assertion fails.
+func (is *Is) ShouldPanic(f func()) {
+	defer func() {
+		r := recover()
+		if r == nil {
+			fail(is, "expected function to panic")
+		}
+	}()
+	f()
+}
+
 // SetOutput changes the message output Writer from the default (os.Stdout).
 // This may be useful if the application under test takes over the console, or
 // if logging to a file is desired.

is_test.go

@@ -162,6 +162,14 @@ func TestIs(t *testing.T) {
 	is.Equal((*testStruct)(nil), &testStruct{})
 	is.Equal(&testStruct{}, (*testStruct)(nil))
 	is.Equal((*testStruct)(nil), (*testStruct)(nil))
+
+	fail = func(is *Is, format string, args ...interface{}) {
+		fmt.Print(decorate(fmt.Sprintf(format, args...)))
+		t.FailNow()
+	}
+	is.ShouldPanic(func() {
+		panic("The sky is falling!")
+	})
 }
 
 func TestIsMsg(t *testing.T) {