How can I assert a BankAccountError.invalidAmount is thrown in Swift tests?

You can use Swift's pattern matching to check the error type. For example, you can use an "if case" or "switch" statement. Here's how you can modify your test:

SWIFTCopied
@Test func depositNegativeAmountThrowsError() {
    let bankAccount = BankAccount(accountNumber: "1234", balance: 500)
    
    #expect("Invalid amount.", performing: {
        try bankAccount.deposit(amount: -100, depositType: .check)
    }, throws: { error in
        if case BankAccountError.invalidAmount(let amount) = error {
            // Optionally, you can assert the amount if needed:
            // XCTAssertEqual(amount, -100)
        } else {
            XCTFail("Expected BankAccountError.invalidAmount but received \(error)")
        }
    })
}

In this snippet, the if case statement checks that the caught error is of type BankAccountError.invalidAmount. If the error doesn't match, the test fails with an appropriate message. This ensures that the correct error type is being thrown by your code.