Add Len()

assert/assertions.go

@@ -324,6 +324,36 @@ func NotEmpty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
 
 }
 
+// getLen try to get length of object.
+// return (false, 0) if impossible.
+func getLen(x interface{}) (ok bool, length int) {
+	v := reflect.ValueOf(x)
+	defer func() {
+		if e := recover(); e != nil {
+			ok = false
+		}
+	}()
+	return true, v.Len()
+}
+
+// Len asserts that the specified object has specific length.
+// Len also fails if the object has a type that len() not accept.
+//
+//    assert.Len(t, mySlice, 3, "The size of slice is not 3")
+//
+// Returns whether the assertion was successful (true) or not (false).
+func Len(t TestingT, object interface{}, length int, msgAndArgs ...interface{}) bool {
+	ok, l := getLen(object)
+	if !ok {
+		return Fail(t, fmt.Sprintf("\"%s\" could not be applied builtin len()", object), msgAndArgs...)
+	}
+
+	if l != length {
+		return Fail(t, fmt.Sprintf("\"%s\" should have %d item(s), but have %d", object, length, l), msgAndArgs...)
+	}
+	return true
+}
+
 // True asserts that the specified value is true.
 //
 //    assert.True(t, myBool, "myBool should be true")

assert/assertions_test.go

@@ -400,6 +400,90 @@ func TestNotEmpty(t *testing.T) {
 	True(t, NotEmpty(mockT, chWithValue), "Channel with values is not empty")
 }
 
+func Test_getLen(t *testing.T) {
+	falseCases := []interface{}{
+		nil,
+		0,
+		true,
+		false,
+		'A',
+		struct{}{},
+	}
+	for _, v := range falseCases {
+		ok, l := getLen(v)
+		False(t, ok, "Expected getLen fail to get length of %#v", v)
+		Equal(t, 0, l, "getLen should return 0 for %#v", v)
+	}
+
+	ch := make(chan int, 5)
+	ch <- 1
+	ch <- 2
+	ch <- 3
+	trueCases := []struct {
+		v interface{}
+		l int
+	}{
+		{[]int{1, 2, 3}, 3},
+		{[...]int{1, 2, 3}, 3},
+		{"ABC", 3},
+		{map[int]int{1: 2, 2: 4, 3: 6}, 3},
+		{ch, 3},
+
+		{[]int{}, 0},
+		{map[int]int{}, 0},
+		{make(chan int), 0},
+
+		{[]int(nil), 0},
+		{map[int]int(nil), 0},
+		{(chan int)(nil), 0},
+	}
+
+	for _, c := range trueCases {
+		ok, l := getLen(c.v)
+		True(t, ok, "Expected getLen success to get length of %#v", c.v)
+		Equal(t, c.l, l)
+	}
+}
+
+func TestLen(t *testing.T) {
+	mockT := new(testing.T)
+
+	False(t, Len(mockT, nil, 0), "nil does not have length")
+	False(t, Len(mockT, 0, 0), "int does not have length")
+	False(t, Len(mockT, true, 0), "true does not have length")
+	False(t, Len(mockT, false, 0), "false does not have length")
+	False(t, Len(mockT, 'A', 0), "Rune does not have length")
+	False(t, Len(mockT, struct{}{}, 0), "Struct does not have length")
+
+	ch := make(chan int, 5)
+	ch <- 1
+	ch <- 2
+	ch <- 3
+
+	cases := []struct {
+		v interface{}
+		l int
+	}{
+		{[]int{1, 2, 3}, 3},
+		{[...]int{1, 2, 3}, 3},
+		{"ABC", 3},
+		{map[int]int{1: 2, 2: 4, 3: 6}, 3},
+		{ch, 3},
+
+		{[]int{}, 0},
+		{map[int]int{}, 0},
+		{make(chan int), 0},
+
+		{[]int(nil), 0},
+		{map[int]int(nil), 0},
+		{(chan int)(nil), 0},
+	}
+
+	for _, c := range cases {
+		True(t, Len(mockT, c.v, c.l), "%#v have %d items", c.v, c.l)
+	}
+}
+
 func TestWithinDuration(t *testing.T) {
 
 	mockT := new(testing.T)

assert/doc.go

@@ -61,6 +61,8 @@
 //
 //    assert.NotEmpty(t, actualObject [, message [, format-args]])
 //
+//    assert.Len(t, actualObject, expectedLength, [, message [, format-args]])
+//
 //    assert.Error(t, errorObject [, message [, format-args]])
 //
 //    assert.NoError(t, errorObject [, message [, format-args]])
@@ -112,6 +114,8 @@
 //
 //    assert.NotEmpty(actualObject [, message [, format-args]])
 //
+//    assert.Len(actualObject, expectedLength, [, message [, format-args]])
+//
 //    assert.Error(errorObject [, message [, format-args]])
 //
 //    assert.NoError(errorObject [, message [, format-args]])

assert/forward_assertions.go

@@ -87,6 +87,16 @@ func (a *Assertions) NotEmpty(object interface{}, msgAndArgs ...interface{}) boo
 	return NotEmpty(a.t, object, msgAndArgs...)
 }
 
+// Len asserts that the specified object has specific length.
+// Len also fails if the object has a type that len() not accept.
+//
+//    assert.Len(mySlice, 3, "The size of slice is not 3")
+//
+// Returns whether the assertion was successful (true) or not (false).
+func (a *Assertions) Len(object interface{}, length int, msgAndArgs ...interface{}) bool {
+	return Len(a.t, object, length, msgAndArgs...)
+}
+
 // True asserts that the specified value is true.
 //
 //    assert.True(myBool, "myBool should be true")

assert/forward_assertions_test.go

@@ -320,6 +320,46 @@ func TestNotEmptyWrapper(t *testing.T) {
 
 }
 
+func TestLenWrapper(t *testing.T) {
+	assert := New(t)
+	mockAssert := New(new(testing.T))
+
+	assert.False(mockAssert.Len(nil, 0), "nil does not have length")
+	assert.False(mockAssert.Len(0, 0), "int does not have length")
+	assert.False(mockAssert.Len(true, 0), "true does not have length")
+	assert.False(mockAssert.Len(false, 0), "false does not have length")
+	assert.False(mockAssert.Len('A', 0), "Rune does not have length")
+	assert.False(mockAssert.Len(struct{}{}, 0), "Struct does not have length")
+
+	ch := make(chan int, 5)
+	ch <- 1
+	ch <- 2
+	ch <- 3
+
+	cases := []struct {
+		v interface{}
+		l int
+	}{
+		{[]int{1, 2, 3}, 3},
+		{[...]int{1, 2, 3}, 3},
+		{"ABC", 3},
+		{map[int]int{1: 2, 2: 4, 3: 6}, 3},
+		{ch, 3},
+
+		{[]int{}, 0},
+		{map[int]int{}, 0},
+		{make(chan int), 0},
+
+		{[]int(nil), 0},
+		{map[int]int(nil), 0},
+		{(chan int)(nil), 0},
+	}
+
+	for _, c := range cases {
+		assert.True(mockAssert.Len(c.v, c.l), "%#v have %d items", c.v, c.l)
+	}
+}
+
 func TestWithinDurationWrapper(t *testing.T) {
 	assert := New(t)
 	mockAssert := New(new(testing.T))