assert.Equal and similar output should be explicit about type inequality

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#322 2 comments 5 reactions 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
go
Domain
testing

Research direction

Start at the assert.Equal entry point and trace the comparison and failure-reporting path for values with different types. Done means assert.Equal and similar assertions report type inequality explicitly, with regression coverage for the Foos-versus-[]Foo example.

Written by the indexing model from the issue text.

Description

In assert.Equal(t, a, b) if a and b do not have the same type, the test will fail, but the output will be the same as a value equality test failure.

It is confusing, because on complex equality assertion, ones might not realize the problem is different type, not unequal values.

Consider this example:

type struct Foo { V int }
type Foos []Foo

assert.Equal(t, Foos{{1}, {2}}, Foos{{1}, {2})

compared to:

assert.Equal(t, Foos{{1}, {2}}, []Foo{{1}, {2})

The second case will fail with a "not equal" message.

Instead, assert.Equal and similar should output an explicit message about type inequality.

cc @abhinav @prashantv @breerly

Dominant language
Go
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