diff --git a/Cargo.lock b/Cargo.lock
index 28bed3b3e..0dec00598 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "actix-codec"
 version = "0.3.0"
@@ -12,7 +14,7 @@ dependencies = [
  "futures-sink",
  "log",
  "pin-project 0.4.28",
- "tokio 0.2.25",
+ "tokio",
  "tokio-util",
 ]
 
@@ -23,7 +25,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "177837a10863f15ba8d3ae3ec12fac1099099529ed20083a27fdfe247381d0dc"
 dependencies = [
  "actix-codec",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-service",
  "actix-utils",
  "derive_more",
@@ -43,7 +45,7 @@ checksum = "452299e87817ae5673910e53c243484ca38be3828db819b6011736fc6982e874"
 dependencies = [
  "actix-codec",
  "actix-connect",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-service",
  "actix-threadpool",
  "actix-utils",
@@ -92,16 +94,6 @@ dependencies = [
  "syn",
 ]
 
-[[package]]
-name = "actix-macros"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2f86cd6857c135e6e9fe57b1619a88d1f94a7df34c00e11fe13e64fd3438837"
-dependencies = [
- "quote",
- "syn",
-]
-
 [[package]]
 name = "actix-router"
 version = "0.2.7"
@@ -121,24 +113,13 @@ version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "143fcc2912e0d1de2bcf4e2f720d2a60c28652ab4179685a1ee159e0fb3db227"
 dependencies = [
- "actix-macros 0.1.3",
+ "actix-macros",
  "actix-threadpool",
  "copyless",
  "futures-channel",
  "futures-util",
  "smallvec",
- "tokio 0.2.25",
-]
-
-[[package]]
-name = "actix-rt"
-version = "2.2.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "bc7d7cd957c9ed92288a7c3c96af81fa5291f65247a76a34dac7b6af74e52ba0"
-dependencies = [
- "actix-macros 0.2.1",
- "futures-core",
- "tokio 1.6.2",
+ "tokio",
 ]
 
 [[package]]
@@ -148,13 +129,13 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "45407e6e672ca24784baa667c5d32ef109ccdd8d5e0b5ebb9ef8a67f4dfb708e"
 dependencies = [
  "actix-codec",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-service",
  "actix-utils",
  "futures-channel",
  "futures-util",
  "log",
- "mio 0.6.23",
+ "mio",
  "mio-uds",
  "num_cpus",
  "slab",
@@ -177,8 +158,8 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "47239ca38799ab74ee6a8a94d1ce857014b2ac36f242f70f3f75a66f691e791c"
 dependencies = [
- "actix-macros 0.1.3",
- "actix-rt 1.1.1",
+ "actix-macros",
+ "actix-rt",
  "actix-server",
  "actix-service",
  "log",
@@ -219,7 +200,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2e9022dec56632d1d7979e59af14f0597a28a830a9c1c7fec8b2327eb9f16b5a"
 dependencies = [
  "actix-codec",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-service",
  "bitflags",
  "bytes 0.5.6",
@@ -240,9 +221,9 @@ checksum = "e641d4a172e7faa0862241a20ff4f1f5ab0ab7c279f00c2d4587b77483477b86"
 dependencies = [
  "actix-codec",
  "actix-http",
- "actix-macros 0.1.3",
+ "actix-macros",
  "actix-router",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-server",
  "actix-service",
  "actix-testing",
@@ -400,7 +381,7 @@ checksum = "b381e490e7b0cfc37ebc54079b0413d8093ef43d14a4e4747083f7fa47a9e691"
 dependencies = [
  "actix-codec",
  "actix-http",
- "actix-rt 1.1.1",
+ "actix-rt",
  "actix-service",
  "base64 0.13.0",
  "bytes 0.5.6",
@@ -1252,7 +1233,7 @@ dependencies = [
  "http",
  "indexmap",
  "slab",
- "tokio 0.2.25",
+ "tokio",
  "tokio-util",
  "tracing",
  "tracing-futures",
@@ -1430,7 +1411,7 @@ dependencies = [
  "itoa",
  "pin-project 1.0.7",
  "socket2",
- "tokio 0.2.25",
+ "tokio",
  "tower-service",
  "tracing",
  "want",
@@ -1741,7 +1722,7 @@ dependencies = [
  "serde_json",
  "shlex",
  "tempfile",
- "tokio 0.2.25",
+ "tokio",
  "toml",
  "warp",
 ]
@@ -1791,25 +1772,12 @@ dependencies = [
  "kernel32-sys",
  "libc",
  "log",
- "miow 0.2.2",
+ "miow",
  "net2",
  "slab",
  "winapi 0.2.8",
 ]
 
-[[package]]
-name = "mio"
-version = "0.7.13"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8c2bdb6314ec10835cd3293dd268473a835c02b7b352e788be788b3c6ca6bb16"
-dependencies = [
- "libc",
- "log",
- "miow 0.3.7",
- "ntapi",
- "winapi 0.3.9",
-]
-
 [[package]]
 name = "mio-extras"
 version = "2.0.6"
@@ -1818,7 +1786,7 @@ checksum = "52403fe290012ce777c4626790c8951324a2b9e3316b3143779c72b029742f19"
 dependencies = [
  "lazycell",
  "log",
- "mio 0.6.23",
+ "mio",
  "slab",
 ]
 
@@ -1830,7 +1798,7 @@ checksum = "afcb699eb26d4332647cc848492bbc15eafb26f08d0304550d5aa1f612e066f0"
 dependencies = [
  "iovec",
  "libc",
- "mio 0.6.23",
+ "mio",
 ]
 
 [[package]]
@@ -1845,15 +1813,6 @@ dependencies = [
  "ws2_32-sys",
 ]
 
-[[package]]
-name = "miow"
-version = "0.3.7"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b9f1c5b025cda876f66ef43a113f91ebc9f4ccef34843000e0adf6ebbab84e21"
-dependencies = [
- "winapi 0.3.9",
-]
-
 [[package]]
 name = "net2"
 version = "0.2.37"
@@ -1913,21 +1872,12 @@ dependencies = [
  "fsevent-sys",
  "inotify",
  "libc",
- "mio 0.6.23",
+ "mio",
  "mio-extras",
  "walkdir",
  "winapi 0.3.9",
 ]
 
-[[package]]
-name = "ntapi"
-version = "0.3.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3f6bb902e437b6d86e03cce10a7e2af662292c5dfef23b65899ea3ac9354ad44"
-dependencies = [
- "winapi 0.3.9",
-]
-
 [[package]]
 name = "num-integer"
 version = "0.1.44"
@@ -2470,6 +2420,18 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
+[[package]]
+name = "replica-server-tests"
+version = "0.3.0"
+dependencies = [
+ "actix-rt",
+ "actix-web",
+ "anyhow",
+ "taskchampion",
+ "taskchampion-sync-server",
+ "tempfile",
+]
+
 [[package]]
 name = "resolv-conf"
 version = "0.7.0"
@@ -3002,7 +2964,7 @@ dependencies = [
 name = "taskchampion-sync-server"
 version = "0.3.0"
 dependencies = [
- "actix-rt 2.2.0",
+ "actix-rt",
  "actix-web",
  "anyhow",
  "clap",
@@ -3209,7 +3171,7 @@ dependencies = [
  "lazy_static",
  "libc",
  "memchr",
- "mio 0.6.23",
+ "mio",
  "mio-uds",
  "pin-project-lite 0.1.12",
  "signal-hook-registry",
@@ -3218,22 +3180,6 @@ dependencies = [
  "winapi 0.3.9",
 ]
 
-[[package]]
-name = "tokio"
-version = "1.6.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aea337f72e96efe29acc234d803a5981cd9a2b6ed21655cd7fc21cfe021e8ec7"
-dependencies = [
- "autocfg",
- "libc",
- "mio 0.7.13",
- "once_cell",
- "parking_lot",
- "pin-project-lite 0.2.6",
- "signal-hook-registry",
- "winapi 0.3.9",
-]
-
 [[package]]
 name = "tokio-macros"
 version = "0.2.6"
@@ -3254,7 +3200,7 @@ dependencies = [
  "futures-util",
  "log",
  "pin-project 0.4.28",
- "tokio 0.2.25",
+ "tokio",
  "tungstenite",
 ]
 
@@ -3269,7 +3215,7 @@ dependencies = [
  "futures-sink",
  "log",
  "pin-project-lite 0.1.12",
- "tokio 0.2.25",
+ "tokio",
 ]
 
 [[package]]
@@ -3351,7 +3297,7 @@ dependencies = [
  "rand 0.7.3",
  "smallvec",
  "thiserror",
- "tokio 0.2.25",
+ "tokio",
  "url",
 ]
 
@@ -3370,7 +3316,7 @@ dependencies = [
  "resolv-conf",
  "smallvec",
  "thiserror",
- "tokio 0.2.25",
+ "tokio",
  "trust-dns-proto",
 ]
 
@@ -3579,7 +3525,7 @@ dependencies = [
  "serde",
  "serde_json",
  "serde_urlencoded 0.6.1",
- "tokio 0.2.25",
+ "tokio",
  "tokio-tungstenite",
  "tower-service",
  "tracing",
diff --git a/Cargo.toml b/Cargo.toml
index cd6520de1..eef6d1ce7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,5 +3,6 @@
 members = [
     "taskchampion",
     "cli",
-    "sync-server"
+    "sync-server",
+    "replica-server-tests"
 ]
diff --git a/README.md b/README.md
index 1b4e1d664..e937b17d2 100644
--- a/README.md
+++ b/README.md
@@ -27,11 +27,12 @@ Assuming that continues, it is unlikely that TaskChampion will ever be recommend
 
 ## Structure
 
-There are three crates here:
+There are four crates here:
 
  * [taskchampion](./taskchampion) - the core of the tool
  * [taskchampion-cli](./cli) - the command-line binary
  * [taskchampion-sync-server](./sync-server) - the server against which `task sync` operates
+ * [replica-server-tests](./replica-server-tests) - the server against which `task sync` operates
 
 ## Documentation Generation
 
diff --git a/cli/Cargo.toml b/cli/Cargo.toml
index feada5597..351e1ecfc 100644
--- a/cli/Cargo.toml
+++ b/cli/Cargo.toml
@@ -3,6 +3,7 @@ authors = ["Dustin J. Mitchell <dustin@mozilla.com>"]
 edition = "2018"
 name = "taskchampion-cli"
 version = "0.3.0"
+publish = false
 
 build = "build.rs"
 
diff --git a/replica-server-tests/Cargo.toml b/replica-server-tests/Cargo.toml
new file mode 100644
index 000000000..c702e4164
--- /dev/null
+++ b/replica-server-tests/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "replica-server-tests"
+version = "0.3.0"
+authors = ["Dustin J. Mitchell <dustin@mozilla.com>"]
+edition = "2018"
+publish = false
+
+[dependencies.taskchampion-sync-server]
+path = "../sync-server"
+
+[dependencies.taskchampion]
+path = "../taskchampion"
+
+[dev-dependencies]
+anyhow = "1.0"
+actix-web = "^3.3.2"
+actix-rt = "^1.1.1"
+tempfile = "3"
diff --git a/replica-server-tests/src/lib.rs b/replica-server-tests/src/lib.rs
new file mode 100644
index 000000000..e783558fc
--- /dev/null
+++ b/replica-server-tests/src/lib.rs
@@ -0,0 +1 @@
+// test-only crate
diff --git a/replica-server-tests/tests/cross-sync.rs b/replica-server-tests/tests/cross-sync.rs
new file mode 100644
index 000000000..a828d0f0d
--- /dev/null
+++ b/replica-server-tests/tests/cross-sync.rs
@@ -0,0 +1,84 @@
+use actix_web::{App, HttpServer};
+use taskchampion::{Replica, ServerConfig, Status, StorageConfig, Uuid};
+use taskchampion_sync_server::{storage::InMemoryStorage, Server};
+
+#[actix_rt::test]
+async fn cross_sync() -> anyhow::Result<()> {
+    let server = Server::new(Box::new(InMemoryStorage::new()));
+    let httpserver =
+        HttpServer::new(move || App::new().service(server.service())).bind("0.0.0.0:0")?;
+
+    // bind was to :0, so the kernel will have selected an unused port
+    let port = httpserver.addrs()[0].port();
+
+    httpserver.run();
+
+    // set up two replicas, and demonstrate replication between them
+    let mut rep1 = Replica::new(StorageConfig::InMemory.into_storage()?);
+    let mut rep2 = Replica::new(StorageConfig::InMemory.into_storage()?);
+
+    let client_key = Uuid::new_v4();
+    let encryption_secret = b"abc123".to_vec();
+    let make_server = || {
+        ServerConfig::Remote {
+            origin: format!("http://127.0.0.1:{}", port),
+            client_key,
+            encryption_secret: encryption_secret.clone(),
+        }
+        .into_server()
+    };
+
+    let mut serv1 = make_server()?;
+    let mut serv2 = make_server()?;
+
+    // add some tasks on rep1
+    let t1 = rep1.new_task(Status::Pending, "test 1".into())?;
+    let t2 = rep1.new_task(Status::Pending, "test 2".into())?;
+
+    // modify t1
+    let mut t1 = t1.into_mut(&mut rep1);
+    t1.start()?;
+    let t1 = t1.into_immut();
+
+    rep1.sync(&mut serv1)?;
+    rep2.sync(&mut serv2)?;
+
+    // those tasks should exist on rep2 now
+    let t12 = rep2
+        .get_task(t1.get_uuid())?
+        .expect("expected task 1 on rep2");
+    let t22 = rep2
+        .get_task(t2.get_uuid())?
+        .expect("expected task 2 on rep2");
+
+    assert_eq!(t12.get_description(), "test 1");
+    assert_eq!(t12.is_active(), true);
+    assert_eq!(t22.get_description(), "test 2");
+    assert_eq!(t22.is_active(), false);
+
+    // make non-conflicting changes on the two replicas
+    let mut t2 = t2.into_mut(&mut rep1);
+    t2.set_status(Status::Completed)?;
+    let t2 = t2.into_immut();
+
+    let mut t12 = t12.into_mut(&mut rep2);
+    t12.set_status(Status::Completed)?;
+
+    // sync those changes back and forth
+    rep1.sync(&mut serv1)?; // rep1 -> server
+    rep2.sync(&mut serv2)?; // server -> rep2, rep2 -> server
+    rep1.sync(&mut serv1)?; // server -> rep1
+
+    let t1 = rep1
+        .get_task(t1.get_uuid())?
+        .expect("expected task 1 on rep1");
+    assert_eq!(t1.get_status(), Status::Completed);
+
+    let t22 = rep2
+        .get_task(t2.get_uuid())?
+        .expect("expected task 2 on rep2");
+    assert_eq!(t22.get_status(), Status::Completed);
+
+    // note that we just drop the server here..
+    Ok(())
+}
diff --git a/sync-server/Cargo.toml b/sync-server/Cargo.toml
index 6c66f6726..ef1442fad 100644
--- a/sync-server/Cargo.toml
+++ b/sync-server/Cargo.toml
@@ -3,6 +3,7 @@ name = "taskchampion-sync-server"
 version = "0.3.0"
 authors = ["Dustin J. Mitchell <dustin@mozilla.com>"]
 edition = "2018"
+publish = false
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
@@ -20,5 +21,5 @@ env_logger = "^0.8.3"
 rusqlite = { version = "0.25", features = ["bundled"] }
 
 [dev-dependencies]
-actix-rt = "^2.2.0"
+actix-rt = "^1.1.1"
 tempfile = "3"