Fix assertion IsNil() failing when passing a nil slice (#94)

* Fixed assertion IsNil() failing when passing a nil slice

* Fixed assertion IsNil() failing when passing a nil slice

* Fixed assertion IsNil() failing when passing a nil slice

* Expand Nil checks to every builtin go type

assertions.go

@@ -91,20 +91,37 @@ func (a *Assertion) IsFalse(messages ...interface{}) {
 	}
 }
 
+// isNil returns whether a.src is nil or not.
+func (a *Assertion) isNil() bool {
+	if !objectsAreEqual(a.src, nil) {
+		specialKinds := []reflect.Kind{
+			reflect.Slice, reflect.Chan,
+			reflect.Map, reflect.Ptr,
+			reflect.Interface, reflect.Func,
+		}
+		t := reflect.TypeOf(a.src).Kind()
+		for _, kind := range specialKinds {
+			if t == kind {
+				return reflect.ValueOf(a.src).IsNil()
+			}
+		}
+		return false
+	}
+	return true
+}
+
 // IsNil asserts that source is nil.
 func (a *Assertion) IsNil(messages ...interface{}) {
-	if !objectsAreEqual(a.src, nil) {
+	if !a.isNil() {
 		message := fmt.Sprintf("%v %s%v", a.src, "expected to be nil", formatMessages(messages...))
-
 		a.fail(message)
 	}
 }
 
 // IsNotNil asserts that source is not nil.
 func (a *Assertion) IsNotNil(messages ...interface{}) {
-	if objectsAreEqual(a.src, nil) {
+	if a.isNil() {
 		message := fmt.Sprintf("%v %s%v", a.src, "is nil", formatMessages(messages...))
-
 		a.fail(message)
 	}
 }

assertions_test.go

@@ -147,15 +147,38 @@ func TestIsTrueWithMessage(t *testing.T) {
 }
 
 func TestIsNil(t *testing.T) {
-	verifier := AssertionVerifier{ShouldPass: true}
-	a := Assertion{src: nil, fail: verifier.FailFunc}
-	a.IsNil()
-	verifier.Verify(t)
+	check := func(isNil interface{}, isNotNil interface{}) {
+		verifier := AssertionVerifier{ShouldPass: true}
+		a := Assertion{src: isNil, fail: verifier.FailFunc}
+		a.IsNil()
+		verifier.Verify(t)
+
+		verifier = AssertionVerifier{ShouldPass: false}
+		a = Assertion{src: isNotNil, fail: verifier.FailFunc}
+		a.IsNil()
+		verifier.Verify(t)
+	}
 
-	verifier = AssertionVerifier{ShouldPass: false}
-	a = Assertion{src: struct{}{}, fail: verifier.FailFunc}
-	a.IsNil()
-	verifier.Verify(t)
+	check(nil, struct {}{})
+
+	var s []struct{}
+	check(s, make([]struct{}, 0))
+
+	var c chan struct{}
+	check(c, make(chan struct{}, 0))
+
+	var m map[struct{}]struct{}
+	check(m, make(map[struct{}]struct{}, 0))
+
+	var p *struct{}
+	check(p, &s)
+
+	var ni interface{} = nil
+	var i interface{} = struct {}{}
+	check(ni, i)
+
+	var f func()
+	check(f, check)
 }
 
 func TestIsNilWithMessage(t *testing.T) {
@@ -167,15 +190,38 @@ func TestIsNilWithMessage(t *testing.T) {
 }
 
 func TestIsNotNil(t *testing.T) {
-	verifier := AssertionVerifier{ShouldPass: true}
-	a := Assertion{src: 1, fail: verifier.FailFunc}
-	a.IsNotNil()
-	verifier.Verify(t)
+	check := func(isNil interface{}, isNotNil interface{}) {
+		verifier := AssertionVerifier{ShouldPass: false}
+		a := Assertion{src: isNil, fail: verifier.FailFunc}
+		a.IsNotNil()
+		verifier.Verify(t)
+
+		verifier = AssertionVerifier{ShouldPass: true}
+		a = Assertion{src: isNotNil, fail: verifier.FailFunc}
+		a.IsNotNil()
+		verifier.Verify(t)
+	}
 
-	verifier = AssertionVerifier{ShouldPass: false}
-	a = Assertion{src: nil, fail: verifier.FailFunc}
-	a.IsNotNil()
-	verifier.Verify(t)
+	check(nil, struct {}{})
+
+	var s []struct{}
+	check(s, make([]struct{}, 0))
+
+	var c chan struct{}
+	check(c, make(chan struct{}, 0))
+
+	var m map[struct{}]struct{}
+	check(m, make(map[struct{}]struct{}, 0))
+
+	var p *struct{}
+	check(p, &s)
+
+	var ni interface{} = nil
+	var i interface{} = struct {}{}
+	check(ni, i)
+
+	var f func()
+	check(f, check)
 }
 
 func TestIsNotNilWithMessage(t *testing.T) {