Add test of Manager using the supplied context function.

Tests the the query being executed uses a context modified by the function.

Also modify reloadRules utility function to take time interval for the
Manager so the test runs faster. We'll work on synthetic clock later.

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

rules/manager_test.go

@@ -817,14 +817,14 @@ func TestUpdateSetsSourceTenants(t *testing.T) {
 	defer ruleManager.Stop()
 
 	rgs, errs := rulefmt.ParseFile("fixtures/rules_with_source_tenants.yaml")
-	require.Equal(t, 0, len(errs), "file parsing failures")
+	require.Empty(t, errs, "file parsing failures")
 
 	tmpFile, err := ioutil.TempFile("", "rules.test.*.yaml")
 	require.NoError(t, err)
 	defer os.Remove(tmpFile.Name())
 	defer tmpFile.Close()
 
-	reloadRules(rgs, t, tmpFile, ruleManager)
+	reloadRules(rgs, t, tmpFile, ruleManager, 0)
 
 	// check that all source tenants were actually set
 	require.Len(t, ruleManager.groups, len(rgs.Groups))
@@ -837,6 +837,55 @@ func TestUpdateSetsSourceTenants(t *testing.T) {
 	}
 }
 
+func TestGroupEvaluationContextFuncIsCalledWhenSupplied(t *testing.T) {
+	type testContextKeyType string
+	var testContextKey testContextKeyType = "TestGroupEvaluationContextFuncIsCalledWhenSupplied"
+	oldContextTestValue := context.Background().Value(testContextKey)
+
+	contextTestValueChannel := make(chan interface{})
+	mockQueryFunc := func(ctx context.Context, qs string, t time.Time) (promql.Vector, error) {
+		contextTestValueChannel <- ctx.Value(testContextKey)
+		return promql.Vector{}, nil
+	}
+
+	mockContextWrapFunc := func(ctx context.Context, g *Group) context.Context {
+		return context.WithValue(ctx, testContextKey, 42)
+	}
+
+	st := teststorage.New(t)
+	defer st.Close()
+
+	ruleManager := NewManager(&ManagerOptions{
+		Appendable:                 st,
+		Queryable:                  st,
+		QueryFunc:                  mockQueryFunc,
+		Context:                    context.Background(),
+		Logger:                     log.NewNopLogger(),
+		GroupEvaluationContextFunc: mockContextWrapFunc,
+	})
+
+	rgs, errs := rulefmt.ParseFile("fixtures/rules_with_source_tenants.yaml")
+	require.Empty(t, errs, "file parsing failures")
+
+	tmpFile, err := ioutil.TempFile("", "rules.test.*.yaml")
+	require.NoError(t, err)
+	defer os.Remove(tmpFile.Name())
+	defer tmpFile.Close()
+
+	// no filesystem is harmed when running this test, set the interval low
+	reloadRules(rgs, t, tmpFile, ruleManager, 10*time.Millisecond)
+
+	ruleManager.start()
+	defer ruleManager.Stop()
+
+	// check that all source tenants were actually set
+	require.Len(t, ruleManager.groups, len(rgs.Groups))
+
+	require.Nil(t, oldContextTestValue, "Context contained test key before the test, impossible")
+	newContextTestValue := <-contextTestValueChannel
+	require.Equal(t, 42, newContextTestValue, "Context does not contain the correct value that should be injected")
+}
+
 // ruleGroupsTest for running tests over rules.
 type ruleGroupsTest struct {
 	Groups []ruleGroupTest `yaml:"groups"`
@@ -879,18 +928,22 @@ func formatRules(r *rulefmt.RuleGroups) ruleGroupsTest {
 	}
 }
 
-func reloadRules(rgs *rulefmt.RuleGroups, t *testing.T, tmpFile *os.File, ruleManager *Manager) {
+func reloadRules(rgs *rulefmt.RuleGroups, t *testing.T, tmpFile *os.File, ruleManager *Manager, interval time.Duration) {
+	if interval == 0 {
+		interval = 10 * time.Second
+	}
+
 	bs, err := yaml.Marshal(formatRules(rgs))
 	require.NoError(t, err)
 	_, _ = tmpFile.Seek(0, 0)
 	_, err = tmpFile.Write(bs)
 	require.NoError(t, err)
-	err = ruleManager.Update(10*time.Second, []string{tmpFile.Name()}, nil, "")
+	err = ruleManager.Update(interval, []string{tmpFile.Name()}, nil, "")
 	require.NoError(t, err)
 }
 
 func reloadAndValidate(rgs *rulefmt.RuleGroups, t *testing.T, tmpFile *os.File, ruleManager *Manager, expected map[string]labels.Labels, ogs map[string]*Group) {
-	reloadRules(rgs, t, tmpFile, ruleManager)
+	reloadRules(rgs, t, tmpFile, ruleManager, 0)
 
 	for h, g := range ruleManager.groups {
 		if ogs[h] == g {