     @uneqDateTimesTZ.exec(@ctx).should.be.true()
 
   it 'should identify uncertain/unequal DateTimes when there is imprecision', ->
-    should(@possiblyEqualDateTimes.exec(@ctx)).be.null
+    should(@possiblyEqualDateTimes.exec(@ctx)).be.null()
     @impossiblyEqualDateTimes.exec(@ctx).should.be.true()
 
 describe 'Less', ->

    @uneqDateTimesTZ.exec(@ctx).should.be.false()

  it 'should identify uncertain/unequal DateTimes when there is imprecision', ->
    should(@possiblyEqualDateTimes.exec(@ctx)).be.null
    @impossiblyEqualDateTimes.exec(@ctx).should.be.false()

describe 'NotEqual', ->

    @aLtB_Quantity_diff.exec(@ctx).should.be.false()

  it 'should be null for 5 Cel >= 4 m', ->
    should(@aGtB_Quantity_incompatible.exec(@ctx)).be.null()

  it 'should be null for 5 Cel >= 5 m', ->
    should(@aEqB_Quantity_incompatible.exec(@ctx)).be.null()

  it 'should be null for 5 Cel >= 40 m', ->
    should(@aLtB_Quantity_incompatible.exec(@ctx)).be.null()

  it 'should be null for 100 [nmi_i] / 2 h > 49 mg/[lb_av]', ->
    should(@divideUcum_incompatible.exec(@ctx)).be.null()

  it 'should be true for 100 mg / 2 [lb_av]  > 49 mg/[lb_av]', ->
    @divideUcum.exec(@ctx).should.be.true()
