XCTAssertEqual fails to compare two string values?

I've just had a similar issue which might help someone.

I have a Float extension function which returns a string. The following test fails:

testValue = 0.01
XCTAssertEqual(testValue.formattedForCost(), "0,01 €")

With the following message:

Assertions: XCTAssertEqual failed: ("Optional("0,01 €")") is not equal to ("Optional("0,01 €")")

Which is rather annoying. However I discovered if I change my test to use the unicode no-break space character:

XCTAssertEqual(testValue.formattedForCost(), "0,01\u{00a0}€")

It passes.

From the documentation of XCTAssertEqual:

Generates a failure when a1 is not equal to a2. This test is for C scalars, structs and unions.

You should use XCTAssertEqualObjects (which uses isEqual: internally) or something like:

XCTAssertTrue([[firstNickName initialsFromString] isEqualToString:expectedResult],
              @"Strings are not equal %@ %@", expectedResult, [firstNickName initialsFromString]);