[Refactor] Check error types in tests.

[arberiii]

What is frustrating you?
Test cases that expect errors usually pass if it has any error, which is not correct if the error is different from what is expected.
For example:
Test case struct has the field:

short/backend/app/usecase/url/urlcreator_test.go

Line 38 in e506d99

expHasErr bool

Then checking the expected behavior is done in this way:

short/backend/app/usecase/url/urlcreator_test.go

Lines 192 to 193 in e506d99

	if testCase.expHasErr {
	assert.NotEqual(t, nil, err)

Your solution
Tests should pass only if the error type is precisely the one expected.

[magicoder10]

https://github.com/short-d/short/pull/796/files#r436382369