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assert.Empty: comprehensive doc of "Empty"-ness rules #1753

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Merged
dolmen merged 1 commit into from
Jun 2, 2025
Merged

assert.Empty: comprehensive doc of "Empty"-ness rules #1753

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16 changes: 12 additions & 4 deletions 16 assert/assertion_format.go
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32 changes: 24 additions & 8 deletions 32 assert/assertion_forward.go
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16 changes: 12 additions & 4 deletions 16 assert/assertions.go
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Original file line number Diff line number Diff line change
Expand Up @@ -773,10 +773,19 @@ func isEmpty(object interface{}) bool {
}
}

// Empty asserts that the specified object is empty. I.e. nil, "", false, 0 or either
// a slice or a channel with len == 0.
// Empty asserts that the given value is "empty".
//
// [Zero values] are "empty".
//
// Arrays are "empty" if every element is the zero value of the type (stricter than "empty").
//
// Slices, maps and channels with zero length are "empty".
//
// Pointer values are "empty" if the pointer is nil or if the pointed value is "empty".
//
// assert.Empty(t, obj)
//
// [Zero values]: https://go.dev/ref/spec#The_zero_value
func Empty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
pass := isEmpty(object)
if !pass {
Expand All @@ -789,8 +798,7 @@ func Empty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
return pass
}

// NotEmpty asserts that the specified object is NOT empty. I.e. not nil, "", false, 0 or either
// a slice or a channel with len == 0.
// NotEmpty asserts that the specified object is NOT [Empty].
//
// if assert.NotEmpty(t, obj) {
// assert.Equal(t, "two", obj[1])
Expand Down
97 changes: 96 additions & 1 deletion 97 assert/assertions_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1728,24 +1728,119 @@ func Test_isEmpty(t *testing.T) {

True(t, isEmpty(""))
True(t, isEmpty(nil))
True(t, isEmpty(error(nil)))
True(t, isEmpty((*int)(nil)))
True(t, isEmpty((*string)(nil)))
True(t, isEmpty(new(string)))
Comment on lines +1731 to +1734

@PeterEFinch PeterEFinch May 29, 2025

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I think your list is pretty extensive.

You could test some interfaces with nil values but have a types associated with them but that might be a bit overkill. For example, you can have err being nil according to the assertions but is not equal to nil

type MyError struct{}

func (e *MyError) Error() string {
	return "my error"
}

func TestMyError_isNil(t *testing.T) {
	var e *MyError
	err := error(e)
	assert.False(t, err == nil)
	assert.Empty(t, err)
	assert.Nil(t, err)
	assert.Zero(t, err)
}

@brackendawson brackendawson May 30, 2025

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Because testify works at runtime it does not have visibility of your code's interface types, they get always converted into interface{}, eg:

var e *MyError // type: *MyError, value: nil
assert.Empty(t, e)
...
func Empty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
	object // type: interface{}, value: (*MyError)(nil)
...
err := error(e) // type: error, value: (*MyError)(nil)
assert.Empty(t, err)
...
func Empty(t TestingT, object interface{}, msgAndArgs ...interface{}) bool {
	object // type: interface{}, value: (*MyError)(nil)

Put simply, testify cannot tell that you passed an interface.

True(t, isEmpty([]string{}))
True(t, isEmpty([]string(nil)))
True(t, isEmpty([]byte(nil)))
True(t, isEmpty([]byte{}))
True(t, isEmpty([]byte("")))
True(t, isEmpty([]bool(nil)))
True(t, isEmpty([]bool{}))
True(t, isEmpty([]interface{}(nil)))
True(t, isEmpty([]interface{}{}))
True(t, isEmpty(struct{}{}))
True(t, isEmpty(&struct{}{}))
True(t, isEmpty(struct{ A int }{A: 0}))
True(t, isEmpty(struct{ a int }{a: 0}))
True(t, isEmpty(struct {
a int
B int
}{a: 0, B: 0}))
True(t, isEmpty(0))
True(t, isEmpty(int(0)))
True(t, isEmpty(int8(0)))
True(t, isEmpty(int16(0)))
True(t, isEmpty(uint16(0)))
True(t, isEmpty(int32(0)))
True(t, isEmpty(uint32(0)))
True(t, isEmpty(int64(0)))
True(t, isEmpty(uint64(0)))
True(t, isEmpty('\u0000')) // rune => int32
True(t, isEmpty(float32(0)))
True(t, isEmpty(float64(0)))
True(t, isEmpty(0i)) // complex
True(t, isEmpty(0.0i)) // complex
True(t, isEmpty(false))
True(t, isEmpty(new(bool)))
True(t, isEmpty(map[string]string{}))
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True(t, isEmpty(map[string]string(nil)))
True(t, isEmpty(new(time.Time)))
True(t, isEmpty(time.Time{}))
True(t, isEmpty(make(chan struct{})))
True(t, isEmpty([1]int{}))
True(t, isEmpty(chan struct{}(nil)))
True(t, isEmpty(chan<- struct{}(nil)))
True(t, isEmpty(make(chan struct{})))
True(t, isEmpty(make(chan<- struct{})))
True(t, isEmpty(make(chan struct{}, 1)))
True(t, isEmpty(make(chan<- struct{}, 1)))
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True(t, isEmpty([1]int{0}))
True(t, isEmpty([2]int{0, 0}))
True(t, isEmpty([8]int{}))
True(t, isEmpty([...]int{7: 0}))
True(t, isEmpty([...]bool{false, false}))
True(t, isEmpty(errors.New(""))) // BEWARE
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True(t, isEmpty([]error{}))
True(t, isEmpty([]error(nil)))
True(t, isEmpty(&[1]int{0}))
True(t, isEmpty(&[2]int{0, 0}))
False(t, isEmpty("something"))
False(t, isEmpty(errors.New("something")))
False(t, isEmpty([]string{"something"}))
False(t, isEmpty(1))
False(t, isEmpty(int(1)))
False(t, isEmpty(uint(1)))
False(t, isEmpty(byte(1)))
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False(t, isEmpty(int8(1)))
False(t, isEmpty(uint8(1)))
False(t, isEmpty(int16(1)))
False(t, isEmpty(uint16(1)))
False(t, isEmpty(int32(1)))
False(t, isEmpty(uint32(1)))
False(t, isEmpty(int64(1)))
False(t, isEmpty(uint64(1)))
False(t, isEmpty('A')) // rune => int32
False(t, isEmpty(true))
False(t, isEmpty(1.0))
False(t, isEmpty(1i)) // complex
False(t, isEmpty([]byte{0})) // elements values are ignored for slices
False(t, isEmpty([]byte{0, 0})) // elements values are ignored for slices
False(t, isEmpty([]string{""})) // elements values are ignored for slices
False(t, isEmpty([]string{"a"})) // elements values are ignored for slices
False(t, isEmpty([]bool{false})) // elements values are ignored for slices
False(t, isEmpty([]bool{true})) // elements values are ignored for slices
False(t, isEmpty([]error{errors.New("xxx")}))
False(t, isEmpty([]error{nil})) // BEWARE
False(t, isEmpty([]error{errors.New("")})) // BEWARE
False(t, isEmpty(map[string]string{"Hello": "World"}))
False(t, isEmpty(map[string]string{"": ""}))
False(t, isEmpty(map[string]string{"foo": ""}))
False(t, isEmpty(map[string]string{"": "foo"}))
False(t, isEmpty(chWithValue))
False(t, isEmpty([1]bool{true}))
False(t, isEmpty([2]bool{false, true}))
False(t, isEmpty([...]bool{10: true}))
False(t, isEmpty([]int{0}))
False(t, isEmpty([]int{42}))
False(t, isEmpty([1]int{42}))
False(t, isEmpty([2]int{0, 42}))
False(t, isEmpty(&[1]int{42}))
False(t, isEmpty(&[2]int{0, 42}))
False(t, isEmpty([1]*int{new(int)})) // array elements must be the zero value, not any Empty value
False(t, isEmpty(struct{ A int }{A: 42}))
False(t, isEmpty(struct{ a int }{a: 42}))
False(t, isEmpty(struct{ a *int }{a: new(int)})) // fields must be the zero value, not any Empty value
False(t, isEmpty(struct{ a []int }{a: []int{}})) // fields must be the zero value, not any Empty value
False(t, isEmpty(struct {
a int
B int
}{a: 0, B: 42}))
False(t, isEmpty(struct {
a int
B int
}{a: 42, B: 0}))
}

func TestEmpty(t *testing.T) {
Expand Down
32 changes: 24 additions & 8 deletions 32 require/require.go
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32 changes: 24 additions & 8 deletions 32 require/require_forward.go
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