tools/src/cts/result: Add more helpers

Add result.List.StatusTree() for building a query.Tree[Status].
Add helpers for serializing results.
Add helpers for merging and de-duplicating results.

Change the interface of result.List.ReplaceDuplicates() so that the
merging function takes a status set instead of a list of results.

Bug: dawn:1342
Change-Id: I77580ec5fd4c8f12109fb6e9e83afea8b740260c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/87240
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>

tools/src/cts/result/result.go

@@ -16,7 +16,11 @@
 package result
 
 import (
+	"bufio"
 	"fmt"
+	"io"
+	"os"
+	"path/filepath"
 	"sort"
 	"strings"
 
@@ -126,29 +130,41 @@ func (l List) TransformTags(f func(Tags) Tags) List {
 // ReplaceDuplicates returns a new list with duplicate test results replaced.
 // When a duplicate is found, the function f is called with the duplicate
 // results. The returned status will be used as the replaced result.
-func (l List) ReplaceDuplicates(f func(List) Status) List {
+func (l List) ReplaceDuplicates(f func(Statuses) Status) List {
 	type key struct {
 		query query.Query
 		tags  string
 	}
-	m := map[key]List{}
+	// Collect all duplicates
+	duplicates := map[key]Statuses{}
 	for _, r := range l {
 		k := key{r.Query, TagsToString(r.Tags)}
-		m[k] = append(m[k], r)
+		if s, ok := duplicates[k]; ok {
-	}
+			s.Add(r.Status)
-	for key, results := range m {
+		} else {
-		if len(results) > 1 {
+			duplicates[k] = NewStatuses(r.Status)
-			result := results[0]
-			result.Status = f(results)
-			m[key] = List{result}
 		}
 	}
-	out := make(List, 0, len(m))
+	// Resolve duplicates
+	merged := map[key]Status{}
+	for key, statuses := range duplicates {
+		if len(statuses) > 1 {
+			merged[key] = f(statuses)
+		} else {
+			merged[key] = statuses.One() // Only one status
+		}
+	}
+	// Rebuild list
+	out := make(List, 0, len(duplicates))
 	for _, r := range l {
 		k := key{r.Query, TagsToString(r.Tags)}
-		if unique, ok := m[k]; ok {
+		if status, ok := merged[k]; ok {
-			out = append(out, unique[0])
+			out = append(out, Result{
-			delete(m, k)
+				Query:  r.Query,
+				Tags:   r.Tags,
+				Status: status,
+			})
+			delete(merged, k) // Remove from map to prevent duplicates
 		}
 	}
 	return out
@@ -201,11 +217,125 @@ func (l List) FilterByTags(tags Tags) List {
 	})
 }
 
+// Statuses is a set of Status
+type Statuses = container.Set[Status]
+
+// NewStatuses returns a new status set with the provided statuses
+func NewStatuses(s ...Status) Statuses { return container.NewSet(s...) }
+
 // Statuses returns a set of all the statuses in the list
-func (l List) Statuses() container.Set[Status] {
+func (l List) Statuses() Statuses {
-	set := container.NewSet[Status]()
+	set := NewStatuses()
 	for _, r := range l {
 		set.Add(r.Status)
 	}
 	return set
 }
+
+// StatusTree is a query tree of statuses
+type StatusTree = query.Tree[Status]
+
+// StatusTree returns a query.Tree from the List, with the Status as the tree
+// node data.
+func (l List) StatusTree() (StatusTree, error) {
+	tree := StatusTree{}
+	for _, r := range l {
+		if err := tree.Add(r.Query, r.Status); err != nil {
+			return StatusTree{}, err
+		}
+	}
+	return tree, nil
+}
+
+// Load loads the result list from the file with the given path
+func Load(path string) (List, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	results, err := Read(file)
+	if err != nil {
+		return nil, fmt.Errorf("while reading '%v': %w", path, err)
+	}
+	return results, nil
+}
+
+// Save saves the result list to the file with the given path
+func Save(path string, results List) error {
+	dir := filepath.Dir(path)
+	if err := os.MkdirAll(dir, 0777); err != nil {
+		return err
+	}
+	file, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	return Write(file, results)
+}
+
+// Read reads a result list from the given reader
+func Read(r io.Reader) (List, error) {
+	scanner := bufio.NewScanner(r)
+	l := List{}
+	for scanner.Scan() {
+		r, err := Parse(scanner.Text())
+		if err != nil {
+			return nil, err
+		}
+		l = append(l, r)
+	}
+	return l, nil
+}
+
+// Write writes a result list to the given writer
+func Write(w io.Writer, l List) error {
+	for _, r := range l {
+		if _, err := fmt.Fprintln(w, r); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Merge merges and sorts two results lists.
+// Duplicates are removed using the Deduplicate() function.
+func Merge(a, b List) List {
+	merged := make(List, 0, len(a)+len(b))
+	merged = append(merged, a...)
+	merged = append(merged, b...)
+	out := merged.ReplaceDuplicates(Deduplicate)
+	out.Sort()
+	return out
+}
+
+// Deduplicate is the standard algorithm used to de-duplicating mixed results.
+// This function is expected to be handed to List.ReplaceDuplicates().
+func Deduplicate(s Statuses) Status {
+	// If all results have the same status, then use that
+	if len(s) == 1 {
+		return s.One()
+	}
+
+	// Mixed statuses. Replace with something appropriate.
+	switch {
+	// Crash + * = Crash
+	case s.Contains(Crash):
+		return Crash
+	// Abort + * = Abort
+	case s.Contains(Abort):
+		return Abort
+	// Unknown + * = Unknown
+	case s.Contains(Unknown):
+		return Unknown
+	// RetryOnFailure + ~(Crash | Abort | Unknown) = RetryOnFailure
+	case s.Contains(RetryOnFailure):
+		return RetryOnFailure
+	// Pass + ~(Crash | Abort | Unknown | RetryOnFailure | Slow) = RetryOnFailure
+	case s.Contains(Pass):
+		return RetryOnFailure
+	}
+	return Unknown
+}

tools/src/cts/result/result_test.go

@@ -15,12 +15,14 @@
 package result_test
 
 import (
+	"bytes"
 	"fmt"
 	"testing"
 
 	"dawn.googlesource.com/dawn/tools/src/container"
 	"dawn.googlesource.com/dawn/tools/src/cts/query"
 	"dawn.googlesource.com/dawn/tools/src/cts/result"
+	"dawn.googlesource.com/dawn/tools/src/utils"
 	"github.com/google/go-cmp/cmp"
 )
 
@@ -304,16 +306,18 @@ func TestTransformTags(t *testing.T) {
 
 func TestReplaceDuplicates(t *testing.T) {
 	type Test struct {
-		results result.List
+		location string
-		fn      func(result.List) result.Status
+		results  result.List
-		expect  result.List
+		fn       func(result.Statuses) result.Status
+		expect   result.List
 	}
 	for _, test := range []Test{
 		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
 			results: result.List{
 				result.Result{Query: Q(`a`), Status: result.Pass},
 			},
-			fn: func(l result.List) result.Status {
+			fn: func(result.Statuses) result.Status {
 				return result.Abort
 			},
 			expect: result.List{
@@ -321,23 +325,25 @@ func TestReplaceDuplicates(t *testing.T) {
 			},
 		},
 		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
 			results: result.List{
 				result.Result{Query: Q(`a`), Status: result.Pass},
 				result.Result{Query: Q(`a`), Status: result.Pass},
 			},
-			fn: func(l result.List) result.Status {
+			fn: func(result.Statuses) result.Status {
 				return result.Abort
 			},
 			expect: result.List{
-				result.Result{Query: Q(`a`), Status: result.Abort},
+				result.Result{Query: Q(`a`), Status: result.Pass},
 			},
 		},
 		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
 			results: result.List{
 				result.Result{Query: Q(`a`), Status: result.Pass},
 				result.Result{Query: Q(`b`), Status: result.Pass},
 			},
-			fn: func(l result.List) result.Status {
+			fn: func(result.Statuses) result.Status {
 				return result.Abort
 			},
 			expect: result.List{
@@ -346,16 +352,14 @@ func TestReplaceDuplicates(t *testing.T) {
 			},
 		},
 		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
 			results: result.List{
 				result.Result{Query: Q(`a`), Status: result.Pass},
 				result.Result{Query: Q(`b`), Status: result.Pass},
 				result.Result{Query: Q(`a`), Status: result.Skip},
 			},
-			fn: func(got result.List) result.Status {
+			fn: func(got result.Statuses) result.Status {
-				expect := result.List{
+				expect := result.NewStatuses(result.Pass, result.Skip)
-					result.Result{Query: Q(`a`), Status: result.Pass},
-					result.Result{Query: Q(`a`), Status: result.Skip},
-				}
 				if diff := cmp.Diff(got, expect); diff != "" {
 					t.Errorf("function's parameter was not as expected:\n%v", diff)
 				}
@@ -369,7 +373,7 @@ func TestReplaceDuplicates(t *testing.T) {
 	} {
 		got := test.results.ReplaceDuplicates(test.fn)
 		if diff := cmp.Diff(got, test.expect); diff != "" {
-			t.Errorf("Results:\n%v\nReplaceDuplicates() was not as expected:\n%v", test.results, diff)
+			t.Errorf("\n%v ReplaceDuplicates() was not as expected:\n%v", test.location, diff)
 		}
 	}
 }
@@ -847,3 +851,322 @@ func TestStatuses(t *testing.T) {
 		}
 	}
 }
+
+func TestStatusTree(t *testing.T) {
+	type Node = query.TreeNode[result.Status]
+	type Children = query.TreeNodeChildren[result.Status]
+	type ChildKey = query.TreeNodeChildKey
+
+	pass := result.Pass
+
+	type Test struct {
+		results   result.List
+		expectErr error
+		expect    result.StatusTree
+	}
+	for _, test := range []Test{
+		{ //////////////////////////////////////////////////////////////////////
+			results: result.List{},
+			expect:  result.StatusTree{},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			results: result.List{
+				{Query: Q(`suite:a:*`), Status: result.Pass},
+			},
+			expect: result.StatusTree{
+				TreeNode: Node{
+					Children: Children{
+						ChildKey{Name: `suite`, Target: query.Suite}: &Node{
+							Query: Q(`suite`),
+							Children: Children{
+								ChildKey{Name: `a`, Target: query.Files}: &Node{
+									Query: Q(`suite:a`),
+									Children: Children{
+										ChildKey{Name: `*`, Target: query.Tests}: &Node{
+											Query: Q(`suite:a:*`),
+											Data:  &pass,
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			results: result.List{
+				{Query: Q(`suite:a:*`), Status: result.Pass},
+				{Query: Q(`suite:a:*`), Status: result.Failure},
+			},
+			expectErr: query.ErrDuplicateData{Query: Q(`suite:a:*`)},
+		},
+	} {
+		got, err := test.results.StatusTree()
+		if diff := cmp.Diff(err, test.expectErr); diff != "" {
+			t.Errorf("Results:\n%v\nStatusTree() error was not as expected:\n%v", test.results, diff)
+			continue
+		}
+		if diff := cmp.Diff(got, test.expect); diff != "" {
+			t.Errorf("Results:\n%v\nStatusTree() was not as expected:\n%v", test.results, diff)
+		}
+	}
+}
+
+func TestReadWrite(t *testing.T) {
+	in := result.List{
+		{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+		{Query: Q(`suite:b,*`), Tags: T(`y`), Status: result.Failure},
+		{Query: Q(`suite:a:b:*`), Tags: T(`x`, `y`), Status: result.Skip},
+		{Query: Q(`suite:a:c,*`), Tags: T(`y`, `x`), Status: result.Failure},
+		{Query: Q(`suite:a,b:c,*`), Tags: T(`y`, `x`), Status: result.Crash},
+		{Query: Q(`suite:a,b:c:*`), Status: result.Slow},
+	}
+	buf := &bytes.Buffer{}
+	if err := result.Write(buf, in); err != nil {
+		t.Fatalf("Write(): %v", err)
+	}
+	got, err := result.Read(buf)
+	if err != nil {
+		t.Fatalf("Read(): %v", err)
+	}
+	if diff := cmp.Diff(got, in); diff != "" {
+		t.Errorf("Read() was not as expected:\n%v", diff)
+	}
+}
+
+func TestMerge(t *testing.T) {
+	type Test struct {
+		location string
+		a, b     result.List
+		expect   result.List
+	}
+	for _, test := range []Test{
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a:        result.List{},
+			b:        result.List{},
+			expect:   result.List{},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			b: result.List{},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a:        result.List{},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			b: result.List{
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`y`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:a:*`), Tags: T(`y`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Status: result.Pass},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Crash},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Crash},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Crash},
+			},
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			a: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:c:*`), Tags: T(`x`), Status: result.Failure},
+				{Query: Q(`suite:d:*`), Tags: T(`x`), Status: result.Failure},
+				{Query: Q(`suite:e:*`), Tags: T(`x`), Status: result.Crash},
+			},
+			b: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.Failure},
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:c:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:d:*`), Tags: T(`y`), Status: result.Pass},
+				{Query: Q(`suite:e:*`), Tags: T(`x`), Status: result.Pass},
+			},
+			expect: result.List{
+				{Query: Q(`suite:a:*`), Tags: T(`x`), Status: result.RetryOnFailure},
+				{Query: Q(`suite:b:*`), Tags: T(`x`), Status: result.Pass},
+				{Query: Q(`suite:c:*`), Tags: T(`x`), Status: result.RetryOnFailure},
+				{Query: Q(`suite:d:*`), Tags: T(`x`), Status: result.Failure},
+				{Query: Q(`suite:d:*`), Tags: T(`y`), Status: result.Pass},
+				{Query: Q(`suite:e:*`), Tags: T(`x`), Status: result.Crash},
+			},
+		},
+	} {
+		got := result.Merge(test.a, test.b)
+		if diff := cmp.Diff(got, test.expect); diff != "" {
+			t.Errorf("%v\nStatusTree() was not as expected:\n%v", test.location, diff)
+		}
+	}
+}
+
+func TestDeduplicate(t *testing.T) {
+	type Test struct {
+		location string
+		statuses result.Statuses
+		expect   result.Status
+	}
+	for _, test := range []Test{
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass),
+			expect:   result.Pass,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Abort),
+			expect:   result.Abort,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Failure),
+			expect:   result.Failure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Skip),
+			expect:   result.Skip,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Crash),
+			expect:   result.Crash,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Slow),
+			expect:   result.Slow,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Unknown),
+			expect:   result.Unknown,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.RetryOnFailure),
+			expect:   result.RetryOnFailure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Failure),
+			expect:   result.RetryOnFailure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Abort),
+			expect:   result.Abort,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Skip),
+			expect:   result.RetryOnFailure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Crash),
+			expect:   result.Crash,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Slow),
+			expect:   result.RetryOnFailure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.Unknown),
+			expect:   result.Unknown,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Pass, result.RetryOnFailure),
+			expect:   result.RetryOnFailure,
+		},
+		{ //////////////////////////////////////////////////////////////////////
+			location: utils.ThisLine(),
+			statuses: result.NewStatuses(result.Status("??"), result.Status("?!")),
+			expect:   result.Unknown,
+		},
+	} {
+		got := result.Deduplicate(test.statuses)
+		if diff := cmp.Diff(got, test.expect); diff != "" {
+			t.Errorf("\n%v Deduplicate() was not as expected:\n%v", test.location, diff)
+		}
+	}
+}

tools/src/cts/result/status.go

@@ -14,6 +14,8 @@
 
 package result
 
+import "dawn.googlesource.com/dawn/tools/src/container"
+
 // Status is an enumerator of test results
 type Status string
 
@@ -28,3 +30,12 @@ const (
 	Slow           = Status("Slow")
 	Unknown        = Status("Unknown")
 )
+
+// CommonStatus is a function that can be used by StatusTree.Reduce() to reduce
+// tree nodes with the same status
+func CommonStatus(statuses []Status) *Status {
+	if set := container.NewSet(statuses...); len(set) == 1 {
+		return &statuses[0]
+	}
+	return nil
+}

tools/src/cts/result/status_test.go

@@ -0,0 +1,54 @@
+// Copyright 2022 The Dawn Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package result_test
+
+import (
+	"testing"
+
+	"dawn.googlesource.com/dawn/tools/src/cts/result"
+	"github.com/google/go-cmp/cmp"
+)
+
+func TestCommonStatus(t *testing.T) {
+	pass := result.Pass
+
+	type Test struct {
+		in     []result.Status
+		expect *result.Status
+	}
+	for _, test := range []Test{
+		{
+			in:     nil,
+			expect: nil,
+		}, {
+			in:     []result.Status{},
+			expect: nil,
+		}, {
+			in:     []result.Status{result.Pass},
+			expect: &pass,
+		}, {
+			in:     []result.Status{result.Pass, result.Pass, result.Pass},
+			expect: &pass,
+		}, {
+			in:     []result.Status{result.Pass, result.Failure, result.Pass},
+			expect: nil,
+		},
+	} {
+		got := result.CommonStatus(test.in)
+		if diff := cmp.Diff(got, test.expect); diff != "" {
+			t.Errorf("%v.CommonStatus('%v') was not as expected:\n%v", test.in, test.expect, diff)
+		}
+	}
+}