diff --git a/tvix/eval/Cargo.lock b/tvix/eval/Cargo.lock
index beba1a7bf..7fec8dac0 100644
--- a/tvix/eval/Cargo.lock
+++ b/tvix/eval/Cargo.lock
@@ -43,6 +43,12 @@ version = "3.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c1ad822118d20d2c234f427000d5acc36eabe1e29a348c89b63dd60b13f28e5d"
 
+[[package]]
+name = "byteorder"
+version = "1.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "14c189c53d098945499cdfa7ecc63567cf3886b3332b312a5b4585d8d3a6a610"
+
 [[package]]
 name = "cast"
 version = "0.3.0"
@@ -309,6 +315,15 @@ dependencies = [
  "str-buf",
 ]
 
+[[package]]
+name = "fastrand"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a7a407cfaa3385c4ae6b23e84623d48c2798d06e3e6a1878f7f59f17b3f86499"
+dependencies = [
+ "instant",
+]
+
 [[package]]
 name = "fd-lock"
 version = "3.0.6"
@@ -364,6 +379,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "instant"
+version = "0.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a5bbe824c507c5da5956355e86a746d82e0e1464f65d862cc5e71da70e94b2c"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "io-lifetimes"
 version = "0.7.3"
@@ -536,6 +560,12 @@ dependencies = [
  "plotters-backend",
 ]
 
+[[package]]
+name = "ppv-lite86"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb9f9e6e233e5c4a35559a617bf40a4ec447db2e84c20b55a6f83167b7e57872"
+
 [[package]]
 name = "pretty_assertions"
 version = "1.3.0"
@@ -566,6 +596,30 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "proptest"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e0d9cc07f18492d879586c92b485def06bc850da3118075cd45d50e9c95b0e5"
+dependencies = [
+ "bitflags",
+ "byteorder",
+ "lazy_static",
+ "num-traits",
+ "quick-error",
+ "rand 0.8.5",
+ "rand_chacha",
+ "rand_xorshift",
+ "regex-syntax",
+ "tempfile",
+]
+
+[[package]]
+name = "quick-error"
+version = "2.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a993555f31e5a609f617c12db6250dedcac1b0a85076912c436e6fc9b2c8e6a3"
+
 [[package]]
 name = "quote"
 version = "0.6.13"
@@ -607,6 +661,27 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "rand"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "34af8d1a0e25924bc5b7c43c079c942339d8f0a8b57c39049bef581b46327404"
+dependencies = [
+ "libc",
+ "rand_chacha",
+ "rand_core 0.6.4",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6c10a63a0fa32252be49d21e7709d4d4baf8d231c2dbce1eaa8141b9b127d88"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "rand_core"
 version = "0.3.1"
@@ -622,6 +697,24 @@ version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c33a3c44ca05fa6f1807d8e6743f3824e8509beca625669633be0acbdf509dc"
 
+[[package]]
+name = "rand_core"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec0be4795e2f6a28069bec0b5ff3e2ac9bafc99e6a9a7dc3547996c5c816922c"
+dependencies = [
+ "getrandom",
+]
+
+[[package]]
+name = "rand_xorshift"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d25bf25ec5ae4a3f1b92f929810509a2f53d7dca2f50b794ff57e3face536c8f"
+dependencies = [
+ "rand_core 0.6.4",
+]
+
 [[package]]
 name = "rayon"
 version = "1.5.3"
@@ -849,6 +942,29 @@ version = "1.0.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9e08d8363704e6c71fc928674353e6b7c23dcea9d82d7012c8faf2a3a025f8d0"
 
+[[package]]
+name = "structmeta"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1bd9c2155aa89fb2c2cb87d99a610c689e7c47099b3e9f1c8a8f53faf4e3d2e3"
+dependencies = [
+ "proc-macro2 1.0.43",
+ "quote 1.0.21",
+ "structmeta-derive",
+ "syn 1.0.99",
+]
+
+[[package]]
+name = "structmeta-derive"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bafede0d0a2f21910f36d47b1558caae3076ed80f6f3ad0fc85a91e6ba7e5938"
+dependencies = [
+ "proc-macro2 1.0.43",
+ "quote 1.0.21",
+ "syn 1.0.99",
+]
+
 [[package]]
 name = "syn"
 version = "0.15.44"
@@ -886,10 +1002,24 @@ version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "15f2b5fb00ccdf689e0149d1b1b3c03fead81c2b37735d812fa8bddbbf41b6d8"
 dependencies = [
- "rand",
+ "rand 0.4.6",
  "remove_dir_all",
 ]
 
+[[package]]
+name = "tempfile"
+version = "3.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5cdb1ef4eaeeaddc8fbd371e5017057064af0911902ef36b39801f67cc6d79e4"
+dependencies = [
+ "cfg-if",
+ "fastrand",
+ "libc",
+ "redox_syscall",
+ "remove_dir_all",
+ "winapi",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.1.3"
@@ -911,6 +1041,18 @@ dependencies = [
  "syn 0.15.44",
 ]
 
+[[package]]
+name = "test-strategy"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62d6408d1406657be2f9d1701fbae379331d30d2f6e92050710edb0d34eeb480"
+dependencies = [
+ "proc-macro2 1.0.43",
+ "quote 1.0.21",
+ "structmeta",
+ "syn 1.0.99",
+]
+
 [[package]]
 name = "text-size"
 version = "1.1.0"
@@ -967,6 +1109,7 @@ dependencies = [
  "itertools",
  "path-clean",
  "pretty_assertions",
+ "proptest",
  "rnix",
  "rowan",
  "rustyline",
@@ -974,6 +1117,7 @@ dependencies = [
  "tabwriter",
  "tempdir",
  "test-generator",
+ "test-strategy",
 ]
 
 [[package]]
diff --git a/tvix/eval/Cargo.toml b/tvix/eval/Cargo.toml
index 5ccfa6328..a8d93ca0e 100644
--- a/tvix/eval/Cargo.toml
+++ b/tvix/eval/Cargo.toml
@@ -21,6 +21,8 @@ tabwriter = "1.2"
 rowan = "*" # pinned by rnix
 codemap = "0.1.3"
 codemap-diagnostic = "0.1.1"
+proptest = { version = "1.0.0", default_features = false, features = ["std", "alloc", "break-dead-code", "tempfile"], optional = true }
+test-strategy = { version = "0.2.1", optional = true }
 
 # rnix has not been released in a while (as of 2022-09-01), we will
 # use it from git.
@@ -36,7 +38,7 @@ itertools = "0.10.3"
 tempdir = "0.3.7"
 
 [features]
-default = [ "repl" ]
+default = [ "repl", "arbitrary" ]
 
 # Enables running the Nix language test suite from the original C++
 # Nix implementation (at version 2.3) against Tvix.
@@ -45,6 +47,9 @@ nix_tests = []
 # Enables building the binary (tvix-eval REPL)
 repl = [ "dep:rustyline" ]
 
+# Enables Arbitrary impls for internal types (required to run tests)
+arbitrary = [ "proptest", "test-strategy" ]
+
 [[bench]]
 name = "eval"
 harness = false