Correct way to assert.Equal structs that contain functions pointers

[bLuka]

Hello,

I'm having troubles comparing objects indirectly referencing function pointers.

For the reference, here's a minimal example:

package main

import (
        "testing"

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

type s struct {
        f func()
}

func TestAssert(t *testing.T) {
        var f = func() {}
        var obj = s{f}

        assert.Equal(t, obj, obj)
}

Testing this code leads to this error:

--- FAIL: TestAssert (0.00s)
    main_test.go:17: 
                Error Trace:    main_test.go:17
                Error:          Not equal: 
                                expected: main.s{f:(func())(0x571380)}
                                actual  : main.s{f:(func())(0x571380)}
                            
                                Diff:
                Test:           TestAssert

In my specific case, this function pointer field comes from a private nested structure I don't have the ability to manipulate.

Is there a way to compare structures indirectly embedding a function pointer?

[brackendawson]

As is mentioned in equal's docs functions are only equal if they are both nil. Looking in the source of the reflect package, any further comparison is apparently not possible in Go.

Unfortunately it looks like you'll need to compare each non-function field individually. If you need to check the function fields then you'll probably need to test code which calls them for state.

[bLuka]

As is mentioned in equal's docs functions are only equal if they are both nil. Looking in the source of the reflect package, any further comparison is apparently not possible in Go.

From what I got, it is not possible to just ignore function pointers, then? I saw github.com/google/go-cmp/cmp allows this by passing options. Is there an equivalent using only testify?

By the way, #535 mentions switching from reflect to go-cmp. It could also solve the issue.

Unfortunately it looks like you'll need to compare each non-function field individually.

It's quite complicated in this very specific case, where the function pointer appears in a 3-levels nested private struct.

[dolmen]

Switching to go-cmp is a no-go: we don't want to add a dependency.

[brackendawson]

It will definitely be worth considering this case when switching to go-cmp, so thanks for linking the issues, hopefully that's picked up. It would almost certainly be something for a testify v2 release, which has been proposed but I'm not sure it's coming any time soon as the maintainers of this project seem quite stretched.

I'm fairly certain there isn't a way to do this using only testify. 😔

[OscarVanL]

I've been having the same problem.

[mauriciosl]

bump
In my case the test spec has an Interface, so I can't manually compare the fields.

[mauriciosl]

bump In my case the test spec has an Interface, so I can't manually compare the fields.

In case anyone has the same problem, I ended up testing the type and then comparing the fields manually

[darkprof83]

Is there a way to compare structures indirectly embedding a function pointer?

require.Equal(fmt.Sprint(tt.wantFunc), fmt.Sprint(actFunc))

solved my problem

//go:build testmode
package mypackagetype 

// need flag
// -tags testmode

type stringFunc struct {
  i int
  f string
}

func NewStringFunc(orig origFunc) stringFunc {
  return stringFunc{i: orig.i, f: fmt.Sprint(orig.f)}
}

require.Equal(NewStringFunc(tt.want), NewStringFunc(act))

[oneumyvakin]

Format to string works for me:

wantStr := fmt.Sprintf("%#v", tt.want)
gotStr := fmt.Sprintf("%#v", got)
assert.Equal(t, wantStr, gotStr)