require.Equal: Comparing time.Time after marshalling and unmarshalling is not correct

[clebs]

When testing sending data that contains a time.Time via JSON the sent data and received data are not equal according to require.Equal.

Sample unit test:

import (
	"encoding/json"
	"log"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

type event struct {
	What string
	When time.Time
}

func TestIt(t *testing.T) {

	send := event{
		What: "My birthday",
		When: time.Now(),
	}

	//test marshaling and sending data
	data, err := json.Marshal(send)
	if err != nil {
		log.Fatal("Could not marshal event.")
	}

	//sending ommitted

	// unmarshal obtained data
	receive := event{}
	err = json.Unmarshal(data, &receive)

	if err != nil {
		log.Fatal("Could not unmarshal event.")
	}

	require.Equal(t, send, receive, "Comparing marshal and unmarshal of time.Time.")

}

Equal diff output:

- When: (time.Time) 2017-09-13 14:54:52.119930466 +0200 CEST m=+0.093164966
+ When: (time.Time) 2017-09-13 14:54:52.119930466 +0200 CEST

A possible solution would be having a special comparison for time.Time fields using for example Unix timestamps.

[zbindenren]

Same issue here.

[szabado]

See golang/go#19502.

To summarize the link: this is how the time package works. Marshalling the time drops the monotonic clock reading, as that only has meaning within the current process. Round trip marshalling and unmarshalling of times will produce different structs.

[ernesto-jimenez]

We should use go-cmp instead of reflect.DeepEqual, which would solve this and some other issues.

There's an issue to track that here: #535

Contributions more than welcome :)

[posener]

Since #535 is kind of stuck, maybe we should add a special case to time.Time?

[ernesto-jimenez]

@posener unfortunately, that would require implementing our own version of go-cmp, since we would have to look for it recursively.

[gomezjdaniel]

Any progress on this?

[Linesmerrill]

We just used go-cmp to do a basic comparison check. Would be nice to have this baked into the assertion library though. 😉 https://godoc.org/github.com/google/go-cmp/cmp

[leoleoasd]

Any progress on this?

[boyan-soubachov]

go-cmp is on the list of possible features for testify v2 (as it would be a breaking change). If there's some way to cleanly fix this problem without breaking backwards compatibility for now, I'd be happy to review and get it merged for v1.7.0. in the mean-time

[leoleoasd]

@boyan-soubachov Maybe we can use the solution of #951 on the require package as well??

[boyan-soubachov]

@boyan-soubachov Maybe we can use the solution of #951 on the require package as well??

The code for require is auto-generated from the assert code. Once that's merged, the fix will also be available in the require package :)

[seantcanavan]

a workaround for me was assert.Equal(t, time1.UnixMillis(), time2.UnixMillis()