public void Unions(int elementCount, [PexAssumeNotNull] KeyValuePair <int, int>[] unions)
{
PexAssume.IsTrue(0 < elementCount);
PexSymbolicValue.Minimize(elementCount);
PexAssume.TrueForAll(
unions,
u => 0 <= u.Key && u.Key < elementCount &&
0 <= u.Value && u.Value < elementCount
);
var target = new ForestDisjointSet <int>();
// fill up with 0..elementCount - 1
for (int i = 0; i < elementCount; i++)
{
target.MakeSet(i);
Assert.IsTrue(target.Contains(i));
Assert.AreEqual(i + 1, target.ElementCount);
Assert.AreEqual(i + 1, target.SetCount);
}
// apply Union for pairs unions[i], unions[i+1]
for (int i = 0; i < unions.Length; i++)
{
var left = unions[i].Key;
var right = unions[i].Value;
var setCount = target.SetCount;
bool unioned = target.Union(left, right);
// should be in the same set now
Assert.IsTrue(target.AreInSameSet(left, right));
// if unioned, the count decreased by 1
PexAssert.ImpliesIsTrue(unioned, () => setCount - 1 == target.SetCount);
}
}
