Just.Railway/Raliway.Tests/Errors/Equality.cs

namespace Raliway.Tests.Errors;

public class Equality
{
    public class Equals_Tests
    {
        [Fact]
        public void Identical_ExpectedErrors_are_equal()
        {
            var a = Error.New("custom_type", "some message");
            var b = Error.New("custom_type", "some message");

            a.Equals(b).ShouldBeTrue();
            b.Equals(a).ShouldBeTrue();
            (a == b).ShouldBeTrue();
        }

        [Fact]
        public void Different_type_ExpectedErrors_are_not_equal()
        {
            var a = Error.New("type_a", "same message");
            var b = Error.New("type_b", "same message");

            a.Equals(b).ShouldBeFalse();
            (a == b).ShouldBeFalse();
            (a != b).ShouldBeTrue();
        }

        [Fact]
        public void Different_message_ExpectedErrors_are_not_equal()
        {
            var a = Error.New("same_type", "message a");
            var b = Error.New("same_type", "message b");

            a.Equals(b).ShouldBeFalse();
            (a == b).ShouldBeFalse();
        }

        [Fact]
        public void Same_Type_and_Message_but_different_ExtensionData_are_still_equal()
        {
            var a = Error.New("type", "msg", new Dictionary<string, string> { ["key"] = "a" });
            var b = Error.New("type", "msg", new Dictionary<string, string> { ["key"] = "b" });

            a.Equals(b).ShouldBeTrue();
            (a == b).ShouldBeTrue();
        }

        [Fact]
        public void ExpectedError_and_ExceptionalError_with_same_Type_and_Message_are_equal()
        {
            Error expected = Error.New("shared_type", "shared message");
            Error exceptional = new ExceptionalError("shared_type", "shared message");

            expected.Equals(exceptional).ShouldBeTrue();
            exceptional.Equals(expected).ShouldBeTrue();
            (expected == exceptional).ShouldBeTrue();
        }

        [Fact]
        public void ManyErrors_with_same_elements_same_order_are_equal()
        {
            var a = Error.Many(Error.New("a"), Error.New("b"), Error.New("c"));
            var b = Error.Many(Error.New("a"), Error.New("b"), Error.New("c"));

            a.Equals(b).ShouldBeTrue();
            (a == b).ShouldBeTrue();
        }

        [Fact]
        public void ManyErrors_with_same_elements_different_order_are_not_equal()
        {
            var a = Error.Many(Error.New("a"), Error.New("b"));
            var b = Error.Many(Error.New("b"), Error.New("a"));

            a.Equals(b).ShouldBeFalse();
            (a == b).ShouldBeFalse();
        }
    }

    public class CompareTo_Tests
    {
        [Fact]
        public void CompareTo_null_returns_minus_one()
        {
            var error = Error.New("type", "msg");

            error.CompareTo(null).ShouldBe(-1);
        }

        [Fact]
        public void CompareTo_same_returns_zero()
        {
            var a = Error.New("type", "msg");
            var b = Error.New("type", "msg");

            a.CompareTo(b).ShouldBe(0);
        }

        [Fact]
        public void CompareTo_different_type_compares_by_type()
        {
            var a = Error.New("aaa", "msg");
            var b = Error.New("bbb", "msg");

            a.CompareTo(b).ShouldBeLessThan(0);
            b.CompareTo(a).ShouldBeGreaterThan(0);
        }

        [Fact]
        public void CompareTo_same_type_different_message_compares_by_message()
        {
            var a = Error.New("type", "aaa");
            var b = Error.New("type", "bbb");

            a.CompareTo(b).ShouldBeLessThan(0);
            b.CompareTo(a).ShouldBeGreaterThan(0);
        }

        [Fact]
        public void ManyErrors_CompareTo_different_length_compares_by_count()
        {
            var shorter = Error.Many(Error.New("a"), Error.New("b"));
            var longer = Error.Many(Error.New("a"), Error.New("b"), Error.New("c"));

            shorter.CompareTo(longer).ShouldBeLessThan(0);
            longer.CompareTo(shorter).ShouldBeGreaterThan(0);
        }

        [Fact]
        public void ManyErrors_CompareTo_same_length_element_by_element()
        {
            var a = Error.Many(Error.New("a"), Error.New("b"));
            var b = Error.Many(Error.New("a"), Error.New("c")); // differs at position 1

            a.CompareTo(b).ShouldBeLessThan(0);
            b.CompareTo(a).ShouldBeGreaterThan(0);
        }
    }

    public class IsSimilarTo_Tests
    {
        [Fact]
        public void Same_Type_IsSimilarTo_returns_true_ignoring_Message()
        {
            var a = Error.New("custom_type", "message one");
            var b = Error.New("custom_type", "message two");

            a.IsSimilarTo(b).ShouldBeTrue();
        }

        [Fact]
        public void Different_Type_IsSimilarTo_returns_false()
        {
            var a = Error.New("type_a", "same message");
            var b = Error.New("type_b", "same message");

            a.IsSimilarTo(b).ShouldBeFalse();
        }

        [Fact]
        public void IsSimilarTo_null_returns_false()
        {
            var error = Error.New("type", "msg");

            error.IsSimilarTo(null!).ShouldBeFalse();
        }

        [Fact]
        public void ManyErrors_IsSimilarTo_different_count_returns_false()
        {
            var a = Error.Many(Error.New("a"), Error.New("b"));
            var b = Error.Many(Error.New("a"), Error.New("b"), Error.New("c"));

            a.IsSimilarTo(b).ShouldBeFalse();
        }

        [Fact]
        public void ManyErrors_IsSimilarTo_same_types_different_messages_returns_true()
        {
            var a = Error.Many(Error.New("type", "msg1"));
            var b = Error.Many(Error.New("type", "msg2"));

            a.IsSimilarTo(b).ShouldBeTrue();
        }

        [Fact]
        public void ManyErrors_IsSimilarTo_different_type_at_same_position_returns_false()
        {
            var a = Error.Many(Error.New("type_a", "msg"), Error.New("type_b", "msg"));
            var b = Error.Many(Error.New("type_a", "msg"), Error.New("type_c", "msg"));

            a.IsSimilarTo(b).ShouldBeFalse();
        }
    }

    public class GetHashCode_Tests
    {
        [Fact]
        public void Equal_errors_have_same_hashcode()
        {
            var a = Error.New("type", "msg");
            var b = Error.New("type", "msg");

            a.GetHashCode().ShouldBe(b.GetHashCode());
        }

        [Fact]
        public void Equal_ManyErrors_have_same_hashcode()
        {
            var a = Error.Many(Error.New("a"), Error.New("b"));
            var b = Error.Many(Error.New("a"), Error.New("b"));

            a.GetHashCode().ShouldBe(b.GetHashCode());
        }

        [Fact]
        public void Empty_ManyErrors_hashcode_is_zero()
        {
            var empty = Error.Many(Array.Empty<Error>());

            empty.GetHashCode().ShouldBe(0);
        }
    }
}