Ensure that time has passed between foo0 and foo1

On Windows, the resolution of time.Now() can be surprisingly low: 15ms
according to the comments in the source of time.Now().

Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>

.github/workflows/windows.yaml

@@ -39,5 +39,5 @@ jobs:
       - name: Unit test
         env:
           SKIP_INTEGRATION_TESTS: 1
-        run: go test -mod=vendor -v ./cache/... ./client/... ./frontend/dockerfile/... ./session/... ./source/... ./util/...
+        run: go test -mod=vendor -v ./cache/... ./client/... ./frontend/dockerfile/... ./session/... ./solver/... ./source/... ./util/...
         working-directory: src/github.com/moby/buildkit

solver/testutil/cachestorage_testsuite.go

@@ -37,12 +37,20 @@ func runStorageTest(t *testing.T, fn func(t *testing.T, st solver.CacheKeyStorag
 
 func testResults(t *testing.T, st solver.CacheKeyStorage) {
 	t.Parallel()
+	timeNow := time.Now()
 	err := st.AddResult("foo", solver.CacheResult{
 		ID:        "foo0",
-		CreatedAt: time.Now(),
+		CreatedAt: timeNow,
 	})
 	require.NoError(t, err)
 
+	// Windows time.Now() resolution can be quite coarse, so frequently
+	// time.Now() will be the same between two nearby calls.
+	if time.Now() == timeNow {
+		time.Sleep(time.Duration(100) * time.Millisecond)
+	}
+	require.NotEqual(t, timeNow, time.Now(), "time has stopped")
+
 	err = st.AddResult("foo", solver.CacheResult{
 		ID:        "foo1",
 		CreatedAt: time.Now(),
@@ -67,7 +75,7 @@ func testResults(t *testing.T, st solver.CacheKeyStorage) {
 	require.True(t, ok)
 	f1, ok := m["foo1"]
 	require.True(t, ok)
-	require.True(t, f0.CreatedAt.Before(f1.CreatedAt))
+	require.True(t, f0.CreatedAt.Before(f1.CreatedAt), "f0.CreatedAt %v was not Before f1.CreatedAt %v", f0.CreatedAt, f1.CreatedAt)
 
 	m = map[string]solver.CacheResult{}
 	err = st.WalkResults("bar", func(r solver.CacheResult) error {