 
   it 'should properly calculate before/after unions', ->
     [x, y] = xy @dIvl.before
-    (x.closed.union(y.closed) == null).should.be.true
-    (x.closed.union(y.open) == null).should.be.true
-    (x.open.union(y.closed) == null).should.be.true
-    (x.open.union(y.open) == null).should.be.true
-    (y.closed.union(x.closed) == null).should.be.true
-    (y.closed.union(x.open) == null).should.be.true
-    (y.open.union(x.closed) == null).should.be.true
-    (y.open.union(x.open) == null).should.be.true
+    should(x.closed.union(y.closed)).be.null
+    should(x.closed.union(y.open)).be.null
+    should(x.open.union(y.closed)).be.null
+    should(x.open.union(y.open)).be.null
+    should(y.closed.union(x.closed)).be.null
+    should(y.closed.union(x.open)).be.null
+    should(y.open.union(x.closed)).be.null
+    should(y.open.union(x.open)).be.null
 
   it 'should properly calculate meets unions', ->
     [x, y] = xy @dIvl.meets
     z = @all2012
     x.closed.union(y.closed).equals(z.closed).should.be.true
-    (x.closed.union(y.open) == null).should.be.true
-    (x.open.union(y.closed) == null).should.be.true
-    (x.open.union(y.open) == null).should.be.true
+    should(x.closed.union(y.open)).be.null
+    should(x.open.union(y.closed)).be.null
+    should(x.open.union(y.open)).be.null
     y.closed.union(x.closed).equals(z.closed).should.be.true
-    (y.closed.union(x.open) == null).should.be.true
-    (y.open.union(x.closed) == null).should.be.true
-    (y.open.union(x.open) == null).should.be.true
+    should(y.closed.union(x.open)).be.null
+    should(y.open.union(x.closed)).be.null
+    should(y.open.union(x.open)).be.null
 
   it 'should properly calculate left/right overlapping unions', ->
     [x, y] = xy @dIvl.overlaps


    x = new Interval(a  ,  e)
    y = new Interval(  b,d  )
    (x.intersect(y).low  == b).should.be.true
    (x.intersect(y).high == d).should.be.true
    (y.intersect(x).low  == b).should.be.true
    (y.intersect(x).high == d).should.be.true

    x = new Interval(a,  d )
    y = new Interval(  b, e)
    (x.intersect(y).low  == b).should.be.true
    (x.intersect(y).high == d).should.be.true
    (y.intersect(x).low  == b).should.be.true
    (y.intersect(x).high == d).should.be.true

    x = new Interval(a,b,   )
    y = new Interval(    d,e)


    x = new Interval(a,  d )
    y = new Interval(  b, e)
    x.except(y).should.eql new Interval(a, b, true, false)
    y.except(x).should.eql new Interval(d, e, false, true)

    x = new Interval(a,b,   )
    y = new Interval(    d,e)
