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Add more String.Concat tests #8052

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Add more String.Concat tests #8052

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96 changes: 89 additions & 7 deletions src/System.Runtime/tests/System/StringTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,8 @@
using System.Collections.Generic;
using System.Globalization;
using System.Runtime.InteropServices;
using System.Threading;
using System.Threading.Tasks;
using Xunit;

namespace System.Tests
Expand Down Expand Up @@ -65,12 +67,12 @@ public static unsafe void Ctor_CharPtr_Int_Int_Invalid()
Assert.Throws<ArgumentOutOfRangeException>("startIndex", () =>
{
fixed (char* value = valueArray) { new string(value, -1, 8); } // Start index < 0
});
});

Assert.Throws<ArgumentOutOfRangeException>("length", () =>
{
fixed (char* value = valueArray) { new string(value, 0, -1); } // Length < 0
});
});

Assert.Throws<ArgumentOutOfRangeException>("ptr", () => new string((char*)null, 0, 1)); // null ptr with non-zero length
}
Expand Down Expand Up @@ -168,56 +170,136 @@ public static void Length(string s, int expected)

public static IEnumerable<object[]> Concat_Strings_TestData()
{
yield return new object[] { new string[0], "" };

yield return new object[] { new string[] { "1" }, "1" };
yield return new object[] { new string[] { null }, "" };
yield return new object[] { new string[] { "" }, "" };

yield return new object[] { new string[] { "1", "2" }, "12" };
yield return new object[] { new string[] { null, "1" }, "1" };
yield return new object[] { new string[] { "", "1" }, "1" };
yield return new object[] { new string[] { "1", null }, "1" };
yield return new object[] { new string[] { "1", "" }, "1" };
yield return new object[] { new string[] { null, null }, "" };
yield return new object[] { new string[] { "", "" }, "" };

yield return new object[] { new string[] { "1", "2", "3" }, "123" };
yield return new object[] { new string[] { null, "1", "2" }, "12" };
yield return new object[] { new string[] { "", "1", "2" }, "12" };
yield return new object[] { new string[] { "1", null, "2" }, "12" };
yield return new object[] { new string[] { "1", "", "2" }, "12" };
yield return new object[] { new string[] { "1", "2", null }, "12" };
yield return new object[] { new string[] { "1", "2", "" }, "12" };
yield return new object[] { new string[] { null, "2", null }, "2" };
yield return new object[] { new string[] { "", "2", "" }, "2" };
yield return new object[] { new string[] { null, null, null }, "" };
yield return new object[] { new string[] { "", "", "" }, "" };

yield return new object[] { new string[] { "1", "2", "3", "4" }, "1234" };
yield return new object[] { new string[] { null, "1", "2", "3" }, "123" };
yield return new object[] { new string[] { "", "1", "2", "3" }, "123" };
yield return new object[] { new string[] { "1", null, "2", "3" }, "123" };
yield return new object[] { new string[] { "1", "", "2", "3" }, "123" };
yield return new object[] { new string[] { "1", "2", null, "3" }, "123" };
yield return new object[] { new string[] { "1", "2", "", "3" }, "123" };
yield return new object[] { new string[] { "1", "2", "3", null }, "123" };
yield return new object[] { new string[] { "1", "2", "3", "" }, "123" };
yield return new object[] { new string[] { "1", null, null, null }, "1" };
yield return new object[] { new string[] { "1", "", "", "" }, "1" };
yield return new object[] { new string[] { null, "1", null, "2" }, "12" };
yield return new object[] { new string[] { "", "1", "", "2" }, "12" };
yield return new object[] { new string[] { null, null, null, null }, "" };
yield return new object[] { new string[] { "", "", "", "" }, "" };

yield return new object[] { new string[] { "1", "2", "3", "4", "5" }, "12345" };
yield return new object[] { new string[] { null, "1", "2", "3", "4" }, "1234" };
yield return new object[] { new string[] { "", "1", "2", "3", "4" }, "1234" };
yield return new object[] { new string[] { "1", null, "2", "3", "4" }, "1234" };
yield return new object[] { new string[] { "1", "", "2", "3", "4" }, "1234" };
yield return new object[] { new string[] { "1", "2", null, "3", "4" }, "1234" };
yield return new object[] { new string[] { "1", "2", "", "3", "4" }, "1234" };
yield return new object[] { new string[] { "1", "2", "3", null, "4" }, "1234" };
yield return new object[] { new string[] { "1", "2", "3", "", "4" }, "1234" };
yield return new object[] { new string[] { "1", "2", "3", "4", null }, "1234" };
yield return new object[] { new string[] { "1", "2", "3", "4", "" }, "1234" };
yield return new object[] { new string[] { "1", null, "3", null, "5" }, "135" };
yield return new object[] { new string[] { "1", "", "3", "", "5" }, "135" };
yield return new object[] { new string[] { null, null, null, null, null }, "" };
yield return new object[] { new string[] { "", "", "", "", "" }, "" };

yield return new object[] { new string[] { "abcd", "efgh", "ijkl", "mnop", "qrst", "uvwx", "yz" }, "abcdefghijklmnopqrstuvwxyz" };
}

[Theory]
[MemberData(nameof(Concat_Strings_TestData))]
public static void Concat_String(string[] values, string expected)
{
Action<string> validate = result =>
{
Assert.Equal(expected, result);
// if (result.Length == 0) Assert.Same(string.Empty, result);
};

if (values.Length == 2)
{
Assert.Equal(expected, string.Concat(values[0], values[1]));
validate(string.Concat(values[0], values[1]));
}
else if (values.Length == 3)
{
Assert.Equal(expected, string.Concat(values[0], values[1], values[2]));
validate(string.Concat(values[0], values[1], values[2]));
}
else if (values.Length == 4)
{
Assert.Equal(expected, string.Concat(values[0], values[1], values[2], values[3]));
validate(string.Concat(values[0], values[1], values[2], values[3]));
}

validate(string.Concat(values));
validate(string.Concat((IEnumerable<string>)values));
}

[Fact]
[OuterLoop] // mini-stress test that likely runs for several seconds
public static void Concat_String_ConcurrencySafe()
{
var inputs = new string[2] { "abc", "def" };
var cts = new CancellationTokenSource();
using (var b = new Barrier(2))
{
// String.Concat(string[]) has a slow path that handles the case where the
// input array is mutated concurrently. Queue two tasks, one that repeatedly
// does concats and the other that mutates the array concurrently. This isn't
// guaranteed to trigger the special case, but it typically does.
Task.WaitAll(
Task.Run(() =>
{
b.SignalAndWait();
while (!cts.IsCancellationRequested)
{
string result = string.Concat(inputs);
Assert.True(result == "abcdef" || result == "abc" || result == "def" || result == "", $"result == {result}");
}
}),
Task.Run(() =>
{
b.SignalAndWait();
try
{
for (int iter = 0; iter < 100000000; iter++)
{
Volatile.Write(ref inputs[0], null);
Volatile.Write(ref inputs[1], null);
Volatile.Write(ref inputs[0], "abc");
Volatile.Write(ref inputs[1], "def");
}
}

finally
{
cts.Cancel();
}
}));
}
Assert.Equal(expected, string.Concat(values));
Assert.Equal(expected, string.Concat((IEnumerable<string>)values));
}

public static IEnumerable<object[]> Concat_Objects_TestData()
Expand Down