diff --git a/Cargo.lock b/Cargo.lock
index 3e75210d..d3421911 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -74,6 +74,12 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "anyhow"
+version = "1.0.75"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a4668cab20f66d8d020e1fbc0ebe47217433c1b6c8f2040faf858554e394ace6"
+
 [[package]]
 name = "async-trait"
 version = "0.1.73"
@@ -85,12 +91,102 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "auto-future"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3c1e7e457ea78e524f48639f551fd79703ac3f2237f5ecccdf4708f8a75ad373"
+
 [[package]]
 name = "autocfg"
 version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
+[[package]]
+name = "axum"
+version = "0.6.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3b829e4e32b91e643de6eafe82b1d90675f5874230191a4ffbc1b336dec4d6bf"
+dependencies = [
+ "async-trait",
+ "axum-core",
+ "axum-macros",
+ "bitflags 1.3.2",
+ "bytes",
+ "futures-util",
+ "http",
+ "http-body",
+ "hyper",
+ "itoa",
+ "matchit",
+ "memchr",
+ "mime",
+ "percent-encoding",
+ "pin-project-lite",
+ "rustversion",
+ "serde",
+ "serde_json",
+ "serde_path_to_error",
+ "serde_urlencoded",
+ "sync_wrapper",
+ "tokio",
+ "tower",
+ "tower-layer",
+ "tower-service",
+]
+
+[[package]]
+name = "axum-core"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "759fa577a247914fd3f7f76d62972792636412fbfd634cd452f6a385a74d2d2c"
+dependencies = [
+ "async-trait",
+ "bytes",
+ "futures-util",
+ "http",
+ "http-body",
+ "mime",
+ "rustversion",
+ "tower-layer",
+ "tower-service",
+]
+
+[[package]]
+name = "axum-macros"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdca6a10ecad987bda04e95606ef85a5417dcaac1a78455242d72e031e2b6b62"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "axum-test"
+version = "12.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d2978d45956c95e1c4ae0aea146a926360ba8faf78b4ab3cbf30451eb0879d9"
+dependencies = [
+ "anyhow",
+ "auto-future",
+ "axum",
+ "bytes",
+ "cookie",
+ "http",
+ "hyper",
+ "reserve-port",
+ "serde",
+ "serde_json",
+ "serde_urlencoded",
+ "smallvec",
+ "tokio",
+ "url",
+]
+
 [[package]]
 name = "backtrace"
 version = "0.3.69"
@@ -279,6 +375,16 @@ dependencies = [
  "windows-sys 0.45.0",
 ]
 
+[[package]]
+name = "cookie"
+version = "0.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7efb37c3e1ccb1ff97164ad95ac1606e8ccd35b3fa0a7d99a304c7f4a428cc24"
+dependencies = [
+ "time",
+ "version_check",
+]
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.9"
@@ -344,6 +450,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "deranged"
+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f2696e8a945f658fd14dc3b87242e6b80cd0f36ff04ea560fa39082368847946"
+
 [[package]]
 name = "digest"
 version = "0.10.7"
@@ -438,6 +550,8 @@ name = "fh"
 version = "0.1.6"
 dependencies = [
  "async-trait",
+ "axum",
+ "axum-test",
  "clap",
  "clap_complete",
  "color-eyre",
@@ -829,6 +943,12 @@ dependencies = [
  "regex-automata 0.1.10",
 ]
 
+[[package]]
+name = "matchit"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0e7465ac9959cc2b1404e8e2367b43684a6d13790fe23056cc8c6c5a6b7bcb94"
+
 [[package]]
 name = "memchr"
 version = "2.6.3"
@@ -1033,6 +1153,26 @@ dependencies = [
  "sha2",
 ]
 
+[[package]]
+name = "pin-project"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fda4ed1c6c173e3fc7a83629421152e01d7b1f9b7f65fb301e490e8cfc656422"
+dependencies = [
+ "pin-project-internal",
+]
+
+[[package]]
+name = "pin-project-internal"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4359fd9c9171ec6e8c62926d6faaf553a8dc3f64e1507e76da7911b4f6a04405"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.13"
@@ -1195,6 +1335,16 @@ dependencies = [
  "winreg",
 ]
 
+[[package]]
+name = "reserve-port"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b212efd3460286cd590149feedd0afabef08ee352445dd6b4452f0d136098a5f"
+dependencies = [
+ "lazy_static",
+ "thiserror",
+]
+
 [[package]]
 name = "ring"
 version = "0.16.20"
@@ -1334,6 +1484,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_path_to_error"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4beec8bce849d58d06238cb50db2e1c417cfeafa4c63f692b15c82b7c80f8335"
+dependencies = [
+ "itoa",
+ "serde",
+]
+
 [[package]]
 name = "serde_urlencoded"
 version = "0.7.1"
@@ -1454,6 +1614,12 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "sync_wrapper"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2047c6ded9c721764247e62cd3b03c09ffc529b2ba5b10ec482ae507a4a70160"
+
 [[package]]
 name = "term"
 version = "0.7.0"
@@ -1495,6 +1661,34 @@ dependencies = [
  "once_cell",
 ]
 
+[[package]]
+name = "time"
+version = "0.3.29"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "426f806f4089c493dcac0d24c29c01e2c38baf8e30f1b716ee37e83d200b18fe"
+dependencies = [
+ "deranged",
+ "itoa",
+ "serde",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef927ca75afb808a4d64dd374f00a2adf8d0fcff8e7b184af886c3c87ec4a3f3"
+
+[[package]]
+name = "time-macros"
+version = "0.2.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ad70d68dba9e1f8aceda7aa6711965dfec1cac869f311a51bd08b3a2ccbce20"
+dependencies = [
+ "time-core",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.6.0"
@@ -1564,6 +1758,28 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "tower"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8fa9be0de6cf49e536ce1851f987bd21a43b771b09473c3549a6c853db37c1c"
+dependencies = [
+ "futures-core",
+ "futures-util",
+ "pin-project",
+ "pin-project-lite",
+ "tokio",
+ "tower-layer",
+ "tower-service",
+ "tracing",
+]
+
+[[package]]
+name = "tower-layer"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c20c8dbed6283a09604c3e69b4b7eeb54e298b8a600d4d5ecb5ad39de609f1d0"
+
 [[package]]
 name = "tower-service"
 version = "0.3.2"
@@ -1577,6 +1793,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ce8c33a8d48bd45d624a6e523445fd21ec13d3653cd51f681abf67418f54eb8"
 dependencies = [
  "cfg-if",
+ "log",
  "pin-project-lite",
  "tracing-attributes",
  "tracing-core",
diff --git a/Cargo.toml b/Cargo.toml
index 277baf97..e7831b7e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -48,3 +48,7 @@ tracing-subscriber = { version = "0.3.17", default-features = false, features =
 ] }
 url = { version = "2.4.0", default-features = false, features = ["serde"] }
 urlencoding = "2.1.3"
+
+[dev-dependencies]
+axum = { version = "0.6.20", features = ["macros"] }
+axum-test = "12.5.0"
diff --git a/src/cli/cmd/convert.rs b/src/cli/cmd/convert.rs
index d8bcb3f1..c56e795a 100644
--- a/src/cli/cmd/convert.rs
+++ b/src/cli/cmd/convert.rs
@@ -614,3 +614,113 @@ async fn convert_github_input_to_flakehub(
 
     Ok(url)
 }
+
+#[cfg(test)]
+mod test {
+    use axum::{extract::Path, response::IntoResponse};
+
+    async fn version(
+        Path((org, project, version)): Path<(String, String, String)>,
+    ) -> axum::response::Response {
+        axum::Json(serde_json::json!({
+            "project": project,
+            "pretty_download_url": format!("http://flakehub-localhost/f/{org}/{project}/{version}.tar.gz"),
+        }))
+        .into_response()
+    }
+
+    async fn no_version(Path((org, project)): Path<(String, String)>) -> axum::response::Response {
+        axum::Json(serde_json::json!({
+            "project": project,
+            "pretty_download_url": format!("http://flakehub-localhost/f/{org}/{project}/*.tar.gz"),
+        }))
+        .into_response()
+    }
+
+    fn test_router() -> axum::Router {
+        let app = axum::Router::new()
+            .route(
+                "/version/:org/:project/:version",
+                axum::routing::get(version),
+            )
+            .route("/f/:org/:project", axum::routing::get(no_version));
+
+        app
+    }
+
+    #[tokio::test]
+    async fn nixpkgs_to_flakehub() {
+        let test_server = axum_test::TestServer::new(test_router().into_make_service()).unwrap();
+        let server_addr = test_server.server_address();
+        let server_url = server_addr.parse().unwrap();
+
+        let input_url = url::Url::parse("github:someorg/somerepo").unwrap();
+        let tarball_url = super::convert_input_to_flakehub(&server_url, input_url)
+            .await
+            .ok()
+            .flatten()
+            .unwrap();
+        assert_eq!(tarball_url.path(), "/f/someorg/somerepo/*.tar.gz");
+    }
+
+    #[tokio::test]
+    async fn nixpkgs_release_to_flakehub() {
+        let test_server = axum_test::TestServer::new(test_router().into_make_service()).unwrap();
+        let server_addr = test_server.server_address();
+        let server_url = server_addr.parse().unwrap();
+
+        let input_url = url::Url::parse("github:nixos/nixpkgs/nixos-23.05").unwrap();
+        let tarball_url = super::convert_input_to_flakehub(&server_url, input_url)
+            .await
+            .ok()
+            .flatten()
+            .unwrap();
+        assert_eq!(tarball_url.path(), "/f/nixos/nixpkgs/0.2305.0.tar.gz");
+    }
+
+    #[tokio::test]
+    async fn test_flake1_convert() {
+        let test_server = axum_test::TestServer::new(test_router().into_make_service()).unwrap();
+        let server_addr = test_server.server_address();
+        let server_url = server_addr.parse().unwrap();
+
+        let convert = super::ConvertSubcommand {
+            flake_path: "".into(),
+            dry_run: true,
+            api_addr: server_url,
+        };
+        let flake_contents = include_str!(concat!(
+            env!("CARGO_MANIFEST_DIR"),
+            "/samples/flake1.test.nix"
+        ));
+        let flake_contents = flake_contents.to_string();
+        let parsed = nixel::parse(flake_contents.clone());
+
+        let (new_flake_contents, flake_compat_input_name) = convert
+            .convert_inputs_to_flakehub(&parsed.expression, &flake_contents)
+            .await
+            .unwrap();
+        let new_flake_contents = convert
+            .make_implicit_nixpkgs_explicit(&parsed.expression, &new_flake_contents)
+            .await
+            .unwrap();
+        let new_flake_contents = convert
+            .fixup_flake_compat_input(&new_flake_contents, flake_compat_input_name.unwrap())
+            .await
+            .unwrap();
+
+        assert!(new_flake_contents.contains(
+            r#"flake-compat.url = "http://flakehub-localhost/f/edolstra/flake-compat/*.tar.gz";"#
+        ));
+        assert!(new_flake_contents.contains("f/nixos/nixpkgs/0.2305.0.tar.gz"));
+
+        let nixpkgs_url_lines: Vec<_> = new_flake_contents
+            .lines()
+            .filter(|line| {
+                line.contains("nixpkgs.url") && line.contains("f/nixos/nixpkgs/0.2305.0.tar.gz")
+            })
+            .collect();
+        let num_nixpkgs_url_lines = nixpkgs_url_lines.iter().count();
+        assert_eq!(num_nixpkgs_url_lines, 1);
+    }
+}