test: add agent info endpoint malfunctioning test cases

.NET has test cases which verify the behavior of traces endpoint, that it works even other endpoints could be having problems like config, telemetry or remote config.

This PR to add similar level of testing coverage.

data-pipeline/src/trace_exporter/mod.rs

@@ -1328,7 +1328,7 @@ mod tests {
                 r#"{
                     "rate_by_service": {
                         "service:foo,env:staging": 1.0,
-                        "service:,env:": 0.8 
+                        "service:,env:": 0.8
                     }
                 }"#,
             );
@@ -1548,7 +1548,7 @@ mod tests {
                     r#"{
                     "rate_by_service": {
                         "service:foo,env:staging": 1.0,
-                        "service:,env:": 0.8 
+                        "service:,env:": 0.8
                     }
                 }"#,
                 );
@@ -1580,7 +1580,7 @@ mod tests {
                 r#"{
                     "rate_by_service": {
                         "service:foo,env:staging": 1.0,
-                        "service:,env:": 0.8 
+                        "service:,env:": 0.8
                     }
                 }"#
                 .to_string()
@@ -1695,7 +1695,7 @@ mod tests {
         let response_body = r#"{
                         "rate_by_service": {
                             "service:foo,env:staging": 1.0,
-                            "service:,env:": 0.8 
+                            "service:,env:": 0.8
                         }
                     }"#;
         let traces_endpoint = server.mock(|when, then| {
@@ -1742,4 +1742,85 @@ mod tests {
         }
         metrics_endpoint.assert_hits(1);
     }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_agent_malfunction_info_4xx() {
+        test_agent_malfunction_info(404, r#"{"error":"Not Found"}"#, Duration::from_secs(0));
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_agent_malfunction_info_5xx() {
+        test_agent_malfunction_info(500, r#"{"error":"Internal Server Error"}"#, Duration::from_secs(0));
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_agent_malfunction_info_timeout() {
+        test_agent_malfunction_info(408, r#"{"error":"Internal Server Error"}"#, Duration::from_secs(600));
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_agent_malfunction_info_wrong_answer() {
+        test_agent_malfunction_info(200, "WRONG_ANSWER", Duration::from_secs(0));
+    }
+
+    fn test_agent_malfunction_info(status: u16, response: &str, delay: Duration) {
+        let server = MockServer::start();
+
+        let mock_traces = server.mock(|when, then| {
+            when.method(POST)
+                .header("Content-type", "application/msgpack")
+                .path("/v0.4/traces");
+            then.status(200).body(
+                r#"{
+                    "rate_by_service": {
+                        "service:test,env:staging": 1.0,
+                    }
+                }"#,
+            );
+        });
+
+        let mock_info = server.mock(|when, then| {
+            when.method(GET).path("/info");
+            then.delay(delay).status(status).body(response);
+        });
+
+        let builder = TraceExporterBuilder::default();
+        let exporter = builder
+            .set_url(&server.url("/"))
+            .set_service("test")
+            .set_env("staging")
+            .set_tracer_version("v0.1")
+            .set_language("nodejs")
+            .set_language_version("1.0")
+            .set_language_interpreter("v8")
+            .set_input_format(TraceExporterInputFormat::V04)
+            .set_output_format(TraceExporterOutputFormat::V04)
+            .enable_stats(Duration::from_secs(10))
+            .build()
+            .unwrap();
+
+        let trace_chunk = vec![Span {
+            duration: 10,
+            ..Default::default()
+        }];
+
+        let data = tinybytes::Bytes::from(rmp_serde::to_vec_named(&vec![trace_chunk]).unwrap());
+
+        // Wait for the info fetcher to get the config
+        while mock_info.hits() == 0 {
+            exporter.runtime.block_on(async {
+                sleep(Duration::from_millis(100)).await;
+            })
+        }
+
+        let _ = exporter.send(data, 1).unwrap();
+
+        exporter.shutdown(None).unwrap();
+
+        mock_traces.assert();
+    }
 }