public void GetHashCode_Success(Expression expression, int expectedHashCode)
{
ExpressionEqualityComparer comparer = new ExpressionEqualityComparer();
int hashCode = comparer.GetHashCode(expression);
Assert.Equal(expectedHashCode, hashCode);
}
/// <summary>
/// Generates test data that can be used as expected data in subsequent runs.
/// The generated file (ExpressionHashCodeTest_Generated.tsv) is put into the build directory and
/// must be copied to the project folder in case of an update).
/// </summary>
/// <returns>The generated test data set.</returns>
private static TestRecord[] GenerateTestData()
{
// generate the expected set of hash codes (file can be used as expected data later on)
ExpressionEqualityComparer comparer = new ExpressionEqualityComparer();
List <TestRecord> records = new List <TestRecord>();
foreach (var expression in TestExpressions)
{
int hashCode = comparer.GetHashCode(expression);
records.Add(
new TestRecord
{
Expression = expression.ToString(),
HashCode = hashCode
});
}
#if WRITE_GENERATED_HASH_CODES_TO_FILE
// write expected data set
string path = Path.GetFullPath("ExpressionHashCodeTest_Generated.tsv");
Helpers.WriteTestData(path, records);
#endif // WRITE_GENERATED_HASH_CODES_TO_FILE
// check whether the generated hash codes are different
// (different expressions may have the same hash code, but it should not happen too often...)
Dictionary <int, string> set = new Dictionary <int, string>();
int duplicateHashCodeCount = 0;
foreach (var record in records)
{
if (set.TryGetValue(record.HashCode, out var other))
{
Console.WriteLine("Detected duplicate hash code ({0}) for expression ({1}) and expression ({2})", record.HashCode, other, record.Expression);
duplicateHashCodeCount++;
continue;
}
set.Add(record.HashCode, record.Expression);
}
// check whether the number of hash code duplicates is below the threshold of 5%
double duplicateHashCodeRatio = (double)duplicateHashCodeCount / records.Count;
Assert.True(duplicateHashCodeRatio < 0.05);
return(records.ToArray());
}
public void Equals_Success()
{
ExpressionEqualityComparer comparer = new ExpressionEqualityComparer();
var expressions = TestExpressions.ToArray();
for (int i = 0; i < expressions.Length; i++)
{
for (int j = 0; j < expressions.Length; j++)
{
bool isEqual = comparer.Equals(expressions[i], expressions[j]);
if (i == j)
{
Assert.True(isEqual, $"Expression {i} {expressions[i]} compared with itself should be equal, but Equals() returns false.");
}
else
{
Assert.False(isEqual, $"Expression {i} {expressions[i]} compared with expression {j} ({expressions[j]}) should not be equal, but Equals() returns true.");
}
}
}
}
