Test to verify no extra delay

Author: purnesh42H

internal/resolver/dns/dns_resolver_test.go

@@ -1290,3 +1290,45 @@ func (s) TestMinResolutionInterval(t *testing.T) {
 r.ResolveNow(resolver.ResolveNowOptions{})
 }
 }
+
+// TestMinResolutionInterval_NoExtraDelay verifies that there is no extra delay
+// between two resolution requests apart from [MinResolutionInterval]
+// i.e. if a request is made after [MinResolutionInterval], it should resolve
+// immediately. Test sets [MinResolutionInterval] to 1 second and calls
+// ResolveNow() 4 times with a wait of 1 second between each request.
+// A correct implementation should resolve all requests without timing out in
+// test duration of 5 seconds.
+func (s) TestMinResolutionInterval_NoExtraDelay(t *testing.T) {
+const target = "foo.bar.com"
+
+overrideResolutionInterval(t, 1*time.Second)
+tr := &testNetResolver{
+hostLookupTable: map[string][]string{
+"foo.bar.com": {"1.2.3.4", "5.6.7.8"},
+},
+txtLookupTable: map[string][]string{
+"_grpc_config.foo.bar.com": txtRecordServiceConfig(txtRecordGood),
+},
+}
+overrideNetResolver(t, tr)
+
+r, stateCh, _ := buildResolverWithTestClientConn(t, target)
+
+wantAddrs := []resolver.Address{{Addr: "1.2.3.4" + colonDefaultPort}, {Addr: "5.6.7.8" + colonDefaultPort}}
+wantSC := scJSON
+
+// set context timeout to test duration of 5 seconds
+// to make sure all 4 resolutions happen successfully
+ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+defer cancel()
+
+// We chose to make 4 requests to strike a balance between coverage and
+// test duration. This number is sufficiently large to validate the
+// behavior across multiple resolution attempts, while also reducing
+// the likelihood of flakiness due to timing issues.
+for i := 0; i < 4; i++ {
+verifyUpdateFromResolver(ctx, t, stateCh, wantAddrs, nil, wantSC)
+time.Sleep(1 * time.Second) // respect resolution rate of 1 second for re-resolve
+r.ResolveNow(resolver.ResolveNowOptions{})
+}
+}