Support func comparison in mocks

Makefile

@@ -23,6 +23,7 @@ generate:
 	go run ./cmd/minimock/minimock.go -i ./tests.formatterAlias -o ./tests/formatter_alias_mock.go
 	go run ./cmd/minimock/minimock.go -i ./tests.formatterType -o ./tests/formatter_type_mock.go
 	go run ./cmd/minimock/minimock.go -i ./tests.reader -o ./tests/reader_mock.go -gr
+	go run ./cmd/minimock/minimock.go -i ./tests.funcCaller -o ./tests/func_caller_mock.go
 
 ./bin:
 	mkdir ./bin

equal.go

@@ -40,6 +40,10 @@ func Equal(a, b interface{}) bool {
 				continue
 			}
 
+			if checkFunctions(aFieldValue, bFieldValue) {
+				continue
+			}
+
 			if !reflect.DeepEqual(aFieldValue, bFieldValue) {
 				return false
 			}
@@ -48,6 +52,10 @@ func Equal(a, b interface{}) bool {
 		return true
 	}
 
+	if checkFunctions(a, b) {
+		return true
+	}
+
 	return reflect.DeepEqual(a, b)
 }
 
@@ -103,3 +111,15 @@ func unexported(field reflect.Value) interface{} {
 func unexportedVal(field reflect.Value) reflect.Value {
 	return reflect.NewAt(field.Type(), unsafe.Pointer(field.UnsafeAddr())).Elem()
 }
+
+// checkFunctions returns true
+func checkFunctions(a, b interface{}) (differs bool) {
+	if a == nil || b == nil {
+		return false
+	}
+	if reflect.TypeOf(a).Kind() != reflect.Func || reflect.TypeOf(b).Kind() != reflect.Func {
+		return false
+	}
+
+	return reflect.ValueOf(a).UnsafePointer() == reflect.ValueOf(b).UnsafePointer()
+}

equal_test.go

@@ -0,0 +1,74 @@
+package minimock
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCheckFunctions(t *testing.T) {
+	t.Parallel()
+	var (
+		validFunc        = func() {}
+		nilFunc   func() = nil
+	)
+
+	tests := []struct {
+		name string
+		a    interface{}
+		b    interface{}
+		want bool
+	}{{
+		name: "one is nil, another is nil func",
+		a:    nil,
+		b:    nilFunc,
+		want: false,
+	}, {
+		name: "arguments are nil",
+		a:    nil,
+		b:    nil,
+		want: false,
+	}, {
+		name: "nil func and nil",
+		a:    nilFunc,
+		b:    nil,
+		want: false,
+	}, {
+		name: "arguments are not functions",
+		a:    1,
+		b:    "string",
+		want: false,
+	}, {
+		name: "both functions are nil",
+		a:    nilFunc,
+		b:    nilFunc,
+		want: true,
+	}, {
+		name: "a is nil",
+		a:    nilFunc,
+		b:    validFunc,
+		want: false,
+	}, {
+		name: "b is nil",
+		a:    validFunc,
+		b:    nilFunc,
+		want: false,
+	}, {
+		name: "functions are anonymous",
+		a:    func() {},
+		b:    func() {},
+		want: false,
+	}, {
+		name: "functions are equal",
+		a:    validFunc,
+		b:    validFunc,
+		want: true,
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			assert.Equal(t, tt.want, checkFunctions(tt.a, tt.b))
+		})
+	}
+}