     y.equals(x).should.be.true
 
   it 'should properly calculate before/after unions', ->
-    (@intBeforeUnion.exec(@ctx) == null).should.be.true
+    should(@intBeforeUnion.exec(@ctx)).be.null
 
   it 'should properly calculate meets unions', ->
     x = @intFullInterval.exec(@ctx)

    y.equals(x).should.be.true

  it 'should properly calculate before/after unions', ->
    (@dateTimeBeforeUnion.exec(@ctx) == null).should.be.true

  it 'should properly calculate meets unions', ->
    x = @dateTimeFullInterval.exec(@ctx)

    setup @, data

   it 'should properly calculate sameAs except', ->
    should(@intSameAsExcept.exec(@ctx)).be.null

  it 'should properly calculate before/after except', ->
    @intBeforeExcept.exec(@ctx).should.eql new Interval(0,4)
