diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml
index 8297d80..993e4ea 100644
--- a/.github/workflows/main.yaml
+++ b/.github/workflows/main.yaml
@@ -16,3 +16,18 @@ jobs:
 
     - name: Run tests
       run: nix run -c ./run-tests.py
+
+  integration_tests:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install Nix
+      uses: cachix/install-nix-action@v12
+      with:
+        nix_path: nixpkgs=channel:nixos-20.09
+
+    - name: Run tests
+      run: |
+        nix run -c ./integration-tests/test-nixpkgs.py -f '<nixpkgs>'
diff --git a/integration-tests/test-nixpkgs.py b/integration-tests/test-nixpkgs.py
new file mode 100755
index 0000000..10e63e0
--- /dev/null
+++ b/integration-tests/test-nixpkgs.py
@@ -0,0 +1,183 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i python
+#!nix-shell -p nixUnstable
+#!nix-shell -p "python3.pkgs.callPackage (fetchFromGitHub {owner = \"rmcgibbo\"; repo = \"adaptive-group-testing\"; rev = \"1b6b2522ec61f01ffd015f7a7731a2be92e12c2b\"; sha256 = \"13rwbjfrj28yx42kvyqikw761jg4x5gi2d4dn7zdvif8cyrbsf1r\"; }) { }"
+
+from __future__ import annotations
+import os
+import subprocess
+import json
+import functools
+from typing import List, Tuple
+from adaptive_group_testing import generalized_binary_splitting
+from tempfile import NamedTemporaryFile
+
+KNOWN_ERROR_ATTRS = set(
+    """acl
+alertmanager-bot
+apostrophe
+attr
+bash
+binutils-unwrapped
+bzip2
+coreutils
+coreutils-full
+coreutils-prefixed
+datadog-agent
+diffutils
+findutils
+gawkInteractive
+gcc-unwrapped
+glibc
+gnugrep
+gnupatch
+gnused
+gnutar
+gzip
+holochain-go
+javaPackages.junit_4_12
+javaPackages.mavenHello_1_0
+javaPackages.mavenHello_1_1
+libgccjit
+manim
+mosdepth
+ne
+nim
+nim-unwrapped
+nimble-unwrapped
+nimlsp
+nimmm
+nrpl
+nuweb
+texlive.combined.scheme-full
+texlive.combined.scheme-medium
+uberwriter
+vimPlugins.fruzzy
+zettlr
+zfsbackup
+""".splitlines()
+)
+
+
+@functools.lru_cache()
+def test_chunk(chunk: Tuple[str, ...], nixpkgs_path: str) -> bool:
+    cmd = (
+        ["nixpkgs-hammer", "-f", nixpkgs_path] + list(chunk)
+    )
+
+    # print("  $ " + " ".join(cmd))
+    p = subprocess.run(
+        cmd,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    )
+    if len(chunk) == 1 and p.returncode == 1:
+        print(p.stdout.decode("utf-8"))
+        print(p.stderr.decode("utf-8"))
+    return p.returncode == 1
+
+
+def nix_eval(attrs: Set[str], nixpkgs_path) -> Dict[str, Any]:
+    # from https://github.com/Mic92/nixpkgs-review/blob/d89dcf354b8a25a69bbf0689b4b68f494de1ed48/nixpkgs_review/nix.py#L92
+    with NamedTemporaryFile(mode="w+", suffix=".nix", delete=False) as nix_expr:
+        print("""nixpkgs-path: attr-json:
+
+    with builtins;
+    let
+    pkgs = import nixpkgs-path { config = { checkMeta = true; allowUnfree = true; }; };
+    lib = pkgs.lib;
+
+    attrs = fromJSON (readFile attr-json);
+    getProperties = name: let
+      attrPath = lib.splitString "." name;
+      pkg = lib.attrByPath attrPath null pkgs;
+      maybePath = builtins.tryEval "${pkg}";
+    in rec {
+      exists = lib.hasAttrByPath attrPath pkgs;
+      broken = !exists || !maybePath.success;
+    };
+    in
+    pkgs.lib.genAttrs attrs getProperties
+        """, file=nix_expr)
+
+    attr_json = NamedTemporaryFile(mode="w+", delete=False)
+    delete = True
+    try:
+        json.dump(list(attrs), attr_json)
+        attr_json.flush()
+        cmd = [
+            "nix",
+            "--experimental-features",
+            "nix-command",
+            "eval",
+            "--json",
+            "--impure",
+            "--expr",
+            f"(import {nix_expr.name} {nixpkgs_path} {attr_json.name})",
+        ]
+
+        try:
+            nix_eval = subprocess.run(
+                cmd, check=True, stdout=subprocess.PIPE, text=True
+            )
+        except subprocess.CalledProcessError:
+            delete = False
+            print(
+                f"{' '.join(cmd)} failed to run, {attr_json.name} was stored inspection"
+            )
+            raise
+
+        return json.loads(nix_eval.stdout)
+    finally:
+        attr_json.close()
+        nix_expr.close()
+        if delete:
+            os.unlink(attr_json.name)
+            os.unlink(nix_expr.name)
+
+
+def get_all_attrs(nixpkgs_path: str) -> Tuple[List[str], List[str]]:
+    qaP_output = subprocess.check_output([
+        "nix-env", "-qaP", "-f", nixpkgs_path, "--system-filter", "x86_64-linux"
+    ], text=True)
+    all_attrs = {e.split()[0] for e in qaP_output.splitlines()}
+    attrs = {key for key, value in nix_eval(all_attrs, nixpkgs_path).items() if not value["broken"]}
+
+    unknown_attrs = attrs - KNOWN_ERROR_ATTRS
+    problematic_attrs = attrs & KNOWN_ERROR_ATTRS
+    return unknown_attrs, problematic_attrs
+
+
+def execute(args: argparse.Namespace):
+    unknown_attrs, problematic_attrs = get_all_attrs(args.file)
+    MAX_CONCURRENT_ATTRS = 2000
+
+    def predicate(attrs):
+        def chunker(seq, size):
+            return (seq[pos : pos + size] for pos in range(0, len(seq), size))
+
+        for chunk in chunker(attrs, MAX_CONCURRENT_ATTRS):
+            if test_chunk(tuple(chunk), args.file):
+                print(f"  Tested {len(chunk)}. Got a failure.")
+                return True
+        print(f"  Tested {len(attrs)}. No failures.")
+        return False
+
+    results1 = generalized_binary_splitting(predicate, unknown_attrs, d=2, verbose=True)
+    results2 = generalized_binary_splitting(predicate, problematic_attrs, d=len(problematic_attrs), verbose=True)
+    print(sorted(set(results1 + results2)))
+
+
+def main():
+    import argparse
+    p = argparse.ArgumentParser()
+    p.add_argument("-f", "--file",
+        help="Path to nixpkgs checkout",
+        default="<nixpkgs>"
+    )
+    args = p.parse_args()
+    return execute(args)
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/nixpkgs-hammer b/tools/nixpkgs-hammer
index 18c01d7..eb67d89 100755
--- a/tools/nixpkgs-hammer
+++ b/tools/nixpkgs-hammer
@@ -350,13 +350,28 @@ if __name__ == "__main__":
         prog="nixpkgs-hammer",
         description="check package expressions for common mistakes",
     )
+
+    def absolutize(p: str) -> Path:
+        if p.startswith("<") and p.endswith(">"):
+            path = subprocess.check_output([
+                "nix",
+                "--experimental-features",
+                "nix-command",
+                "eval",
+                "--impure",
+                "--expr",
+                p
+            ], text=True)
+            return Path(path.strip())
+        return Path(p).resolve(strict=True)
+
     parser.add_argument(
         "-f",
         "--file",
         dest="nix_file",
         metavar="FILE",
         # Absolutize so we can refer to it from Nix.
-        type=lambda p: Path(p).resolve(strict=True),
+        type=absolutize,
         # Nix defaults to current directory when file not specified.
         default=Path.cwd(),
         help=(