diff --git a/proxy/tests/support/mod.rs b/proxy/tests/support/mod.rs
index 21f6a951e..9d232d70e 100644
--- a/proxy/tests/support/mod.rs
+++ b/proxy/tests/support/mod.rs
@@ -30,6 +30,71 @@ use self::tower_h2::{Body, RecvBody};
 use std::net::SocketAddr;
 pub use std::time::Duration;
 
+/// Environment variable for overriding the test patience.
+pub const ENV_TEST_PATIENCE_MS: &'static str = "RUST_TEST_PATIENCE_MS";
+pub const DEFAULT_TEST_PATIENCE: Duration = Duration::from_millis(15);
+
+/// Retry an assertion up to a specified number of times, waiting
+/// `RUST_TEST_PATIENCE_MS` between retries.
+///
+/// If the assertion is successful after a retry, execution will continue
+/// normally. If all retries are exhausted and the assertion still fails,
+/// `assert_eventually!` will panic as though a regular `assert!` had failed.
+/// Note that other panics elsewhere in the code under test will not be
+/// prevented.
+///
+/// This should be used sparingly, but is often useful in end-to-end testing
+/// where a desired state may not be reached immediately. For example, when
+/// some state updates asynchronously and there's no obvious way for the test
+/// to wait for an update to occur before making assertions.
+///
+/// The `RUST_TEST_PATIENCE_MS` environment variable may be used to customize
+/// the backoff duration between retries. This may be useful for purposes such
+/// compensating for decreased performance on CI.
+#[macro_export]
+macro_rules! assert_eventually {
+    ($cond:expr, retries: $retries:expr, $($arg:tt)+) => {
+        {
+            use std::{env, u64};
+            use std::time::{Instant, Duration};
+            use std::str::FromStr;
+            // TODO: don't do this *every* time eventually is called (lazy_static?)
+            let patience = env::var($crate::support::ENV_TEST_PATIENCE_MS).ok()
+                .map(|s| {
+                    let millis = u64::from_str(&s)
+                        .expect(
+                            "Could not parse RUST_TEST_PATIENCE_MS environment \
+                             variable."
+                        );
+                    Duration::from_millis(millis)
+                })
+                .unwrap_or($crate::support::DEFAULT_TEST_PATIENCE);
+            let start_t = Instant::now();
+            for i in 0..($retries + 1) {
+                if $cond {
+                    break;
+                } else if i == $retries {
+                    panic!(
+                        "assertion failed after {:?} (retried {} times): {}",
+                        start_t.elapsed(), i, format_args!($($arg)+)
+                    )
+                } else {
+                    ::std::thread::sleep(patience);
+                }
+            }
+        }
+    };
+    ($cond:expr, $($arg:tt)+) => {
+        assert_eventually!($cond, retries: 5, $($arg)+)
+    };
+    ($cond:expr, retries: $retries:expr) => {
+        assert_eventually!($cond, retries: $retries, stringify!($cond))
+    };
+    ($cond:expr) => {
+        assert_eventually!($cond, retries: 5, stringify!($cond))
+    };
+}
+
 pub mod client;
 pub mod controller;
 pub mod proxy;
@@ -64,3 +129,9 @@ impl Stream for RecvBodyStream {
 pub fn s(bytes: &[u8]) -> &str {
     ::std::str::from_utf8(bytes.as_ref()).unwrap()
 }
+
+#[test]
+#[should_panic]
+fn assert_eventually() {
+    assert_eventually!(false)
+}
diff --git a/proxy/tests/telemetry.rs b/proxy/tests/telemetry.rs
index da4e4f6ea..8c7d1dbff 100644
--- a/proxy/tests/telemetry.rs
+++ b/proxy/tests/telemetry.rs
@@ -1,6 +1,7 @@
 #[macro_use]
 extern crate log;
 
+#[macro_use]
 mod support;
 use self::support::*;
 
@@ -262,13 +263,11 @@ fn telemetry_report_errors_are_ignored() {}
 
 macro_rules! assert_contains {
     ($scrape:expr, $contains:expr) => {
-        assert!($scrape.contains($contains), "metrics scrape:\n{:8}\ndid not contain:\n{:8}", $scrape, $contains)
+        assert_eventually!($scrape.contains($contains), "metrics scrape:\n{:8}\ndid not contain:\n{:8}", $scrape, $contains)
     }
 }
 
-// https://github.com/runconduit/conduit/issues/613
 #[test]
-#[cfg_attr(not(feature = "flaky_tests"), ignore)]
 fn metrics_endpoint_inbound_request_count() {
     let _ = env_logger::try_init();
 
@@ -291,15 +290,12 @@ fn metrics_endpoint_inbound_request_count() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // after seeing a request, the request count should be 1.
-    assert_contains!(scrape, "request_total{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\"} 1");
+    assert_contains!(metrics.get("/metrics"), "request_total{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\"} 1");
 
 }
 
-// https://github.com/runconduit/conduit/issues/613
 #[test]
-#[cfg_attr(not(feature = "flaky_tests"), ignore)]
 fn metrics_endpoint_outbound_request_count() {
     let _ = env_logger::try_init();
 
@@ -324,9 +320,8 @@ fn metrics_endpoint_outbound_request_count() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // after seeing a request, the request count should be 1.
-    assert_contains!(scrape, "request_total{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\"} 1");
+    assert_contains!(metrics.get("/metrics"), "request_total{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\"} 1");
 
 }
 
@@ -385,9 +380,7 @@ mod response_classification {
             })
     }
 
-    // https://github.com/runconduit/conduit/issues/613
     #[test]
-    #[cfg_attr(not(feature = "flaky_tests"), ignore)]
     fn inbound_http() {
         let _ = env_logger::try_init();
         let srv = make_test_server().run();
@@ -408,18 +401,15 @@ mod response_classification {
             );
             assert_eq!(&request.status(), status);
 
-            let scrape = metrics.get("/metrics");
             for status in &STATUSES[0..i] {
                 // assert that the current status code is incremented, *and* that
                 // all previous requests are *not* incremented.
-                assert_contains!(scrape, &expected_metric(status, "inbound"))
+                assert_contains!(metrics.get("/metrics"), &expected_metric(status, "inbound"))
             }
         }
     }
 
-    // https://github.com/runconduit/conduit/issues/613
     #[test]
-    #[cfg_attr(not(feature = "flaky_tests"), ignore)]
     fn outbound_http() {
         let _ = env_logger::try_init();
         let srv = make_test_server().run();
@@ -442,11 +432,10 @@ mod response_classification {
             );
             assert_eq!(&request.status(), status);
 
-            let scrape = metrics.get("/metrics");
             for status in &STATUSES[0..i] {
                 // assert that the current status code is incremented, *and* that
                 // all previous requests are *not* incremented.
-                assert_contains!(scrape, &expected_metric(status, "outbound"))
+                assert_contains!(metrics.get("/metrics"), &expected_metric(status, "outbound"))
             }
         }
     }
@@ -479,13 +468,12 @@ fn metrics_endpoint_inbound_response_latency() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // assert the >=1000ms bucket is incremented by our request with 500ms
     // extra latency.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 1");
     // the histogram's count should be 1.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\"} 1");
     // TODO: we're not going to make any assertions about the
     // response_latency_ms_sum stat, since its granularity depends on the actual
@@ -496,46 +484,44 @@ fn metrics_endpoint_inbound_response_latency() {
     info!("client.get(/hi)");
     assert_eq!(client.get("/hi"), "good morning");
 
-    let scrape = metrics.get("/metrics");
+
 
     // request with 40ms extra latency should fall into the 50ms bucket.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 1");
     // 1000ms bucket should be incremented as well, since it counts *all*
     // bservations less than or equal to 1000ms, even if they also increment
     // other buckets.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 2");
     // the histogram's total count should be 2.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\"} 2");
 
     info!("client.get(/hi)");
     assert_eq!(client.get("/hi"), "good morning");
 
-    let scrape = metrics.get("/metrics");
     // request with 40ms extra latency should fall into the 50ms bucket.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 2");
     // 1000ms bucket should be incremented as well.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 3");
     // the histogram's total count should be 3.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\"} 3");
 
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // 50ms bucket should be un-changed by the request with 500ms latency.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 2");
     // 1000ms bucket should be incremented.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 4");
     // the histogram's total count should be 4.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\",classification=\"success\",status_code=\"200\"} 4");
 }
 
@@ -568,13 +554,12 @@ fn metrics_endpoint_outbound_response_latency() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // assert the >=1000ms bucket is incremented by our request with 500ms
     // extra latency.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 1");
     // the histogram's count should be 1.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\"} 1");
     // TODO: we're not going to make any assertions about the
     // response_latency_ms_sum stat, since its granularity depends on the actual
@@ -585,46 +570,42 @@ fn metrics_endpoint_outbound_response_latency() {
     info!("client.get(/hi)");
     assert_eq!(client.get("/hi"), "good morning");
 
-    let scrape = metrics.get("/metrics");
-
     // request with 40ms extra latency should fall into the 50ms bucket.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 1");
     // 1000ms bucket should be incremented as well, since it counts *all*
     // bservations less than or equal to 1000ms, even if they also increment
     // other buckets.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 2");
     // the histogram's total count should be 2.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\"} 2");
 
     info!("client.get(/hi)");
     assert_eq!(client.get("/hi"), "good morning");
 
-    let scrape = metrics.get("/metrics");
     // request with 40ms extra latency should fall into the 50ms bucket.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 2");
     // 1000ms bucket should be incremented as well.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 3");
     // the histogram's total count should be 3.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\"} 3");
 
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
     // 50ms bucket should be un-changed by the request with 500ms latency.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"50\"} 2");
     // 1000ms bucket should be incremented.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_bucket{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\",le=\"1000\"} 4");
     // the histogram's total count should be 4.
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "response_latency_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\",classification=\"success\",status_code=\"200\"} 4");
 }
 
@@ -652,16 +633,14 @@ fn metrics_endpoint_inbound_request_duration() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "request_duration_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\"} 1");
 
     // request without body should also increment request_duration
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "request_duration_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"inbound\"} 2");
 }
 
@@ -689,15 +668,13 @@ fn metrics_endpoint_outbound_request_duration() {
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "request_duration_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\"} 1");
 
     info!("client.get(/hey)");
     assert_eq!(client.get("/hey"), "hello");
 
-    let scrape = metrics.get("/metrics");
-    assert_contains!(scrape,
+    assert_contains!(metrics.get("/metrics"),
         "request_duration_ms_count{authority=\"tele.test.svc.cluster.local\",direction=\"outbound\"} 2");
 }