public void Return_WithSatisfiedConstraint_UndropsTheRowAsExpected()
{
var puzzle = new Puzzle(4);
var matrix = new ExactCoverMatrix(puzzle);
new RowUniquenessConstraint().Constrain(puzzle, matrix);
new ColumnUniquenessConstraint().Constrain(puzzle, matrix);
int valueIndex = 0;
Square square = matrix.GetSquare(new Coordinate(0, 0));
PossibleValue possibleValue = square.GetPossibleValue(valueIndex);
Link linkA = possibleValue.FirstLink;
Link linkB = linkA.Right;
ConstraintHeader constraintA = linkA.Constraint;
ConstraintHeader constraintB = linkB.Constraint;
Assert.True(constraintB.TrySatisfyFrom(possibleValue.FirstLink.Right.Up));
possibleValue.Return();
Assert.Equal(4, square.NumPossibleValues);
Assert.Equal(PossibleSquareState.UNKNOWN, possibleValue.State);
Assert.Equal(4, constraintA.Count);
Assert.Equal(4, constraintB.Count);
Assert.Contains(linkA, constraintA.GetLinks());
Assert.Contains(linkB, constraintB.GetLinks());
}
internal bool TrySatisfyConstraint() => Constraint.TrySatisfyFrom(this);