approximate floating point values when comparing tables

equate floating point values using a combination of
absolute error and ULP (unit of least precision)

execute/executetest/result.go

@@ -1,6 +1,9 @@
 package executetest
 
 import (
+	"fmt"
+
+	"github.com/google/go-cmp/cmp"
 	"github.com/influxdata/flux"
 )
 
@@ -50,3 +53,47 @@ func (ti *TableIterator) Do(f func(flux.Table) error) error {
 	}
 	return nil
 }
+
+// EqualResults compares two lists of Flux Results for equlity
+func EqualResults(want, got []flux.Result) (bool, error) {
+	if len(want) != len(got) {
+		return false, fmt.Errorf("unexpected number of results - want %d results, got %d results", len(want), len(got))
+	}
+	for i, result := range want {
+		w := result
+		g := got[i]
+		if w.Name() != g.Name() {
+			return false, fmt.Errorf("unexpected result name - want %s, got %s", w.Name(), g.Name())
+		}
+		var wt, gt []*Table
+		if err := w.Tables().Do(func(tbl flux.Table) error {
+			t, err := ConvertTable(tbl)
+			if err != nil {
+				return err
+			}
+			wt = append(wt, t)
+			return nil
+		}); err != nil {
+			return false, err
+		}
+		if err := g.Tables().Do(func(tbl flux.Table) error {
+			t, err := ConvertTable(tbl)
+			if err != nil {
+				return err
+			}
+			gt = append(gt, t)
+			return nil
+		}); err != nil {
+			return false, err
+		}
+		NormalizeTables(wt)
+		NormalizeTables(gt)
+		if len(wt) != len(gt) {
+			return false, fmt.Errorf("unexpected size for result %s - want %d tables, got %d tables", w.Name(), len(wt), len(gt))
+		}
+		if !cmp.Equal(wt, gt, floatOptions) {
+			return false, fmt.Errorf("unexpected tables -want/+got\n%s", cmp.Diff(wt, gt))
+		}
+	}
+	return true, nil
+}

execute/executetest/table.go

@@ -3,10 +3,9 @@ package executetest
 import (
 	"fmt"
 
-	"github.com/influxdata/flux/semantic"
-
 	"github.com/influxdata/flux"
 	"github.com/influxdata/flux/execute"
+	"github.com/influxdata/flux/semantic"
 	"github.com/influxdata/flux/values"
 )
 

execute/executetest/transformation.go

@@ -1,15 +1,49 @@
 package executetest
 
 import (
+	"math"
 	"sort"
 	"testing"
 
+	"github.com/gonum/floats"
+
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
+
 	"github.com/influxdata/flux"
 	"github.com/influxdata/flux/execute"
 )
 
+// Two floating point values are considered
+// equal if they are within tol of each other.
+const tol float64 = 1e-25
+
+// The maximum number of floating point values that are allowed
+// to lie between two float64s and still be considered equal.
+const ulp uint = 2
+
+// Comparison options for floating point values.
+// NaNs are considered equal, and float64s must
+// be sufficiently close to be considered equal.
+var floatOptions = cmp.Options{
+	cmpopts.EquateNaNs(),
+	cmp.FilterValues(func(x, y float64) bool {
+		return !math.IsNaN(x) && !math.IsNaN(y)
+	}, cmp.Comparer(func(x, y float64) bool {
+		// If sufficiently close, then move on.
+		// This avoids situations close to zero.
+		if floats.EqualWithinAbs(x, y, tol) {
+			return true
+		}
+		// If not sufficiently close, both floats
+		// must be within ulp steps of each other.
+		if !floats.EqualWithinULP(x, y, ulp) {
+			return false
+		}
+		return true
+	})),
+}
+
 func ProcessTestHelper(
 	t *testing.T,
 	data []flux.Table,
@@ -50,7 +84,7 @@ func ProcessTestHelper(
 	sort.Sort(SortedTables(got))
 	sort.Sort(SortedTables(want))
 
-	if !cmp.Equal(want, got, cmpopts.EquateNaNs()) {
+	if !cmp.Equal(want, got, floatOptions) {
 		t.Errorf("unexpected tables -want/+got\n%s", cmp.Diff(want, got))
 	}
 }

go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db // indirect
 	github.com/gonum/blas v0.0.0-20180125090452-e7c5890b24cf // indirect
 	github.com/gonum/diff v0.0.0-20180125090814-f0137a19aa16 // indirect
-	github.com/gonum/floats v0.0.0-20180125090339-7de1f4ea7ab5 // indirect
+	github.com/gonum/floats v0.0.0-20180125090339-7de1f4ea7ab5
 	github.com/gonum/integrate v0.0.0-20180125090255-09c2f478329f // indirect
 	github.com/gonum/internal v0.0.0-20180125090855-fda53f8d2571 // indirect
 	github.com/gonum/lapack v0.0.0-20180125091020-f0b8b25edece // indirect