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|
package testing_test
import (
"fmt"
"log"
"github.com/juju/loggo/v2"
"github.com/juju/testing"
)
type ExampleInterfaceToMock interface {
Add(a, b int) int
Div(a, b int) (int, error)
}
type fakeType struct {
ExampleInterfaceToMock
*testing.CallMocker
}
func (f *fakeType) Add(a, b int) int {
results := f.MethodCall(f, "Add", a, b)
return results[0].(int)
}
func (f *fakeType) Div(a, b int) (int, error) {
results := f.MethodCall(f, "Div", a, b)
return results[0].(int), testing.TypeAssertError(results[1])
}
type ExampleTypeWhichUsesInterface struct {
calculator ExampleInterfaceToMock
}
func (e *ExampleTypeWhichUsesInterface) Add(nums ...int) int {
var tally int
for n := range nums {
tally = e.calculator.Add(tally, n)
}
return tally
}
func (e *ExampleTypeWhichUsesInterface) Div(nums ...int) (int, error) {
var tally int
var err error
for n := range nums {
tally, err = e.calculator.Div(tally, n)
if err != nil {
break
}
}
return tally, err
}
func Example() {
var logger loggo.Logger
// Set a fake type which mocks out calls.
mock := &fakeType{CallMocker: testing.NewCallMocker(logger)}
mock.Call("Add", 1, 1).Returns(2)
mock.Call("Div", 1, 1).Returns(1, nil)
mock.Call("Div", 1, 0).Returns(0, fmt.Errorf("cannot divide by zero"))
// Pass in the mock which satisifes a dependency of
// ExampleTypeWhichUsesInterface. This allows us to inject mocked
// calls.
example := ExampleTypeWhichUsesInterface{calculator: mock}
if example.Add(1, 1) != 2 {
log.Fatal("unexpected result")
}
if result, err := example.Div(1, 1); err != nil {
log.Fatalf("unexpected error: %v", err)
} else if result != 1 {
log.Fatal("unexpected result")
}
if _, err := example.Div(1, 0); err == nil {
log.Fatal("did not receive expected divide by zero error")
}
}
|
