unit test for context value logging

This reuses the setup code and checks in the benchmark functions.

examples/benchmarks/contextvalues_test.go

@@ -107,10 +107,10 @@ func useContext(ctx context.Context, j, mod, v int) {
 
 const expectedOutput = `{"logger":"","level":0,"msg":"ping","i":1,"j":2,"string":"hello world","int":1,"float":1}`
 
-func discardWithV(b *testing.B, v int) logr.Logger {
+func discardWithV(tb testing.TB, v int) logr.Logger {
 	logger := funcr.NewJSON(func(actualOutput string) {
 		if actualOutput != expectedOutput {
-			b.Fatalf("expected %s, got %s", expectedOutput, actualOutput)
+			tb.Fatalf("expected %s, got %s", expectedOutput, actualOutput)
 		}
 		calls++
 	}, funcr.Options{
@@ -123,3 +123,15 @@ func discardWithV(b *testing.B, v int) logr.Logger {
 }
 
 var calls int64
+
+func TestFromContext(t *testing.T) {
+	ctx := logr.NewContext(context.Background(), discardWithV(t, 1))
+	defer func() {
+		expected := int64(1)
+		if calls != expected {
+			t.Errorf("expected %d calls to Info, got %d", expected, calls)
+		}
+		calls = 0
+	}()
+	newContext(ctx, 0, 1, 0)
+}