diff --git a/Cargo.toml b/Cargo.toml
index 946421a..96fdbf1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,11 +32,13 @@ console_error_panic_hook = { version = "0.1.6", optional = true }
 #
 # Unfortunately, `wee_alloc` requires nightly Rust when targeting wasm for now.
 wee_alloc = { version = "0.4.5", optional = true }
-pretty_assertions = "1.2.1"
 clap = { version = "3.1.9", features = ["derive"] }
 
 [dev-dependencies]
 wasm-bindgen-test = "0.3.13"
+expect-test = "1.2.2"
+pretty_assertions = "1.2.1"
+md5 = "0.7.0"
 
 [profile.release]
 
diff --git a/test_data/gully_cut.md5 b/test_data/gully_cut.md5
new file mode 100644
index 0000000..6fd1f2d
--- /dev/null
+++ b/test_data/gully_cut.md5
@@ -0,0 +1 @@
+01a19f4b08fdc92708a1dcae8df340f4
\ No newline at end of file
diff --git a/tests/snapshot.rs b/tests/snapshot.rs
new file mode 100644
index 0000000..72e889f
--- /dev/null
+++ b/tests/snapshot.rs
@@ -0,0 +1,19 @@
+use democutter::cut;
+use expect_test::{expect_file, ExpectFile};
+use std::fs;
+
+fn snapshot(path: &str, expect: ExpectFile) {
+    let file = fs::read(path).unwrap();
+    let output = cut(&file, 30000, 50000);
+    let output_md5 = md5::compute(&output);
+
+    expect.assert_eq(&format!("{:x}", output_md5));
+}
+
+#[test]
+fn snapshot_gully() {
+    snapshot(
+        "test_data/gully.dem",
+        expect_file!["../test_data/gully_cut.md5"],
+    );
+}