TestAuthenticationChain chain = new TestAuthenticationChain();
        chain.loadResult = null;
        User inputUser = createTestUser("inputuser", "Input User");

        User result = chain.load(inputUser);

        assertNull(result);
        assertEquals(1, chain.loadCalls.size());
        assertEquals(inputUser, chain.loadCalls.get(0));
    }

    // Test load with multiple calls

	}
}

// TestSignV4TrimAll - tests the logic of TrimAll() function
func TestSignV4TrimAll(t *testing.T) {
	testCases := []struct {
		// Input.
		inputStr string
		// Expected result.
		result string
	}{
		{"本語", "本語"},
		{" abc ", "abc"},
		{" a b ", "a b"},
		{"a b ", "a b"},
		{"a  b", "a b"},
		{"a   b", "a b"},
		{"   a   b  c   ", "a b c"},