diff --git a/deployment/check/basic/constants.nix b/deployment/check/basic/constants.nix
index 3cf28d8f..f2573fb8 100644
--- a/deployment/check/basic/constants.nix
+++ b/deployment/check/basic/constants.nix
@@ -5,4 +5,5 @@
   ];
   pathToRoot = ../../..;
   pathFromRoot = ./.;
+  useFlake = true;
 }
diff --git a/deployment/check/basic/nixosTest.nix b/deployment/check/basic/nixosTest.nix
index 93c8ad23..10ed196f 100644
--- a/deployment/check/basic/nixosTest.nix
+++ b/deployment/check/basic/nixosTest.nix
@@ -1,4 +1,9 @@
-{ inputs, lib, ... }:
+{
+  inputs,
+  lib,
+  config,
+  ...
+}:
 
 {
   _class = "nixosTest";
@@ -8,6 +13,7 @@
   sourceFileset = lib.fileset.unions [
     ./constants.nix
     ./deployment.nix
+    (config.pathToCwd + "/flake-under-test.nix")
   ];
 
   nodes.deployer =
diff --git a/deployment/check/cli/constants.nix b/deployment/check/cli/constants.nix
index ce3b5e4d..a48d9076 100644
--- a/deployment/check/cli/constants.nix
+++ b/deployment/check/cli/constants.nix
@@ -8,4 +8,5 @@
   pathToRoot = ../../..;
   pathFromRoot = ./.;
   enableAcme = true;
+  useFlake = true;
 }
diff --git a/deployment/check/cli/nixosTest.nix b/deployment/check/cli/nixosTest.nix
index d171a182..f7f1cf2d 100644
--- a/deployment/check/cli/nixosTest.nix
+++ b/deployment/check/cli/nixosTest.nix
@@ -1,6 +1,7 @@
 {
   inputs,
   hostPkgs,
+  config,
   lib,
   ...
 }:
@@ -19,6 +20,7 @@ in
   sourceFileset = lib.fileset.unions [
     ./constants.nix
     ./deployments.nix
+    (config.pathToCwd + "/flake-under-test.nix")
 
     # REVIEW: I would like to be able to grab all of `/deployment` minus
     # `/deployment/check`, but I can't because there is a bunch of other files
diff --git a/deployment/check/common/nixosTest.nix b/deployment/check/common/nixosTest.nix
index bc30edba..93bd3fef 100644
--- a/deployment/check/common/nixosTest.nix
+++ b/deployment/check/common/nixosTest.nix
@@ -76,8 +76,6 @@ in
       ./sharedOptions.nix
       ./targetNode.nix
       ./targetResource.nix
-
-      (config.pathToCwd + "/flake-under-test.nix")
     ];
 
     acmeNodeIP = config.nodes.acme.networking.primaryIPAddress;
@@ -164,31 +162,38 @@ in
           deployer.succeed(f"echo '{host_key}' > ${config.pathFromRoot}/${tm}_host_key.pub")
         '')}
 
-      ## NOTE: This is super slow. It could probably be optimised in Nix, for
-      ## instance by allowing to grab things directly from the host's store.
-      ##
-      ## NOTE: We use the repository as-is (cf `src` above), overriding only
-      ## `flake.nix` by our `flake-under-test.nix`. We also override the flake
-      ## lock file to use locally available inputs, as we cannot download them.
-      ##
-      with subtest("Override the flake and its lock"):
-        deployer.succeed("cp ${config.pathFromRoot}/flake-under-test.nix flake.nix")
-        deployer.succeed("""
-          nix flake lock --extra-experimental-features 'flakes nix-command' \
-            --offline -v \
-            --override-input nixops4 ${inputs.nixops4.packages.${system}.flake-in-a-bottle} \
-            \
-            --override-input nixops4-nixos ${inputs.nixops4-nixos} \
-            --override-input nixops4-nixos/flake-parts ${inputs.nixops4-nixos.inputs.flake-parts} \
-            --override-input nixops4-nixos/flake-parts/nixpkgs-lib ${inputs.nixops4-nixos.inputs.flake-parts.inputs.nixpkgs-lib} \
-            --override-input nixops4-nixos/nixops4-nixos ${emptyFlake} \
-            --override-input nixops4-nixos/nixpkgs ${inputs.nixops4-nixos.inputs.nixpkgs} \
-            --override-input nixops4-nixos/nixops4 ${
-              inputs.nixops4-nixos.inputs.nixops4.packages.${system}.flake-in-a-bottle
-            } \
-            --override-input nixops4-nixos/git-hooks-nix ${emptyFlake} \
-            ;
-        """)
+      ${
+        if config.useFlake then
+          ''
+            ## NOTE: This is super slow. It could probably be optimised in Nix, for
+            ## instance by allowing to grab things directly from the host's store.
+            ##
+            ## NOTE: We use the repository as-is (cf `src` above), overriding only
+            ## `flake.nix` by our `flake-under-test.nix`. We also override the flake
+            ## lock file to use locally available inputs, as we cannot download them.
+            ##
+            with subtest("Override the flake and its lock"):
+              deployer.succeed("cp ${config.pathFromRoot}/flake-under-test.nix flake.nix")
+              deployer.succeed("""
+                nix flake lock --extra-experimental-features 'flakes nix-command' \
+                  --offline -v \
+                  --override-input nixops4 ${inputs.nixops4.packages.${system}.flake-in-a-bottle} \
+                  \
+                  --override-input nixops4-nixos ${inputs.nixops4-nixos} \
+                  --override-input nixops4-nixos/flake-parts ${inputs.nixops4-nixos.inputs.flake-parts} \
+                  --override-input nixops4-nixos/flake-parts/nixpkgs-lib ${inputs.nixops4-nixos.inputs.flake-parts.inputs.nixpkgs-lib} \
+                  --override-input nixops4-nixos/nixops4-nixos ${emptyFlake} \
+                  --override-input nixops4-nixos/nixpkgs ${inputs.nixops4-nixos.inputs.nixpkgs} \
+                  --override-input nixops4-nixos/nixops4 ${
+                    inputs.nixops4-nixos.inputs.nixops4.packages.${system}.flake-in-a-bottle
+                  } \
+                  --override-input nixops4-nixos/git-hooks-nix ${emptyFlake} \
+                  ;
+              """)
+          ''
+        else
+          ""
+      }
 
       ${optionalString config.enableAcme ''
         with subtest("Set up handmade DNS"):
diff --git a/deployment/check/common/sharedOptions.nix b/deployment/check/common/sharedOptions.nix
index 7201a8f5..c0efc6cf 100644
--- a/deployment/check/common/sharedOptions.nix
+++ b/deployment/check/common/sharedOptions.nix
@@ -64,5 +64,7 @@ in
         during the test to the correct value.
       '';
     };
+
+    useFlake = lib.mkEnableOption "Use a flake in the test.";
   };
 }
diff --git a/deployment/check/data-model/common-nixosTest.nix b/deployment/check/data-model/common-nixosTest.nix
deleted file mode 100644
index aa912dc3..00000000
--- a/deployment/check/data-model/common-nixosTest.nix
+++ /dev/null
@@ -1,168 +0,0 @@
-{
-  inputs,
-  lib,
-  config,
-  hostPkgs,
-  sources,
-  ...
-}:
-
-let
-  inherit (builtins)
-    concatStringsSep
-    toJSON
-    ;
-  inherit (lib)
-    types
-    fileset
-    mkOption
-    genAttrs
-    attrNames
-    optionalString
-    ;
-  inherit (hostPkgs)
-    writeText
-    ;
-
-  forConcat = xs: f: concatStringsSep "\n" (map f xs);
-
-in
-{
-  _class = "nixosTest";
-
-  imports = [
-    ../common/sharedOptions.nix
-  ];
-
-  options = {
-    ## FIXME: I wish I could just use `testScript` but with something like
-    ## `mkOrder` to put this module's string before something else.
-    extraTestScript = mkOption { };
-
-    sourceFileset = mkOption {
-      ## REVIEW: Upstream to nixpkgs?
-      type = types.mkOptionType {
-        name = "fileset";
-        description = "fileset";
-        descriptionClass = "noun";
-        check = (x: (builtins.tryEval (fileset.unions [ x ])).success);
-        merge = (_: defs: fileset.unions (map (x: x.value) defs));
-      };
-      description = ''
-        A fileset that will be copied to the deployer node in the current
-        working directory. This should contain all the files that are
-        necessary to run that particular test, such as the NixOS
-        modules necessary to evaluate a deployment.
-      '';
-    };
-  };
-
-  config = {
-    sourceFileset = fileset.unions [
-      ../../../mkFlake.nix
-      ../../../flake.lock
-      ../../../npins
-      ../../data-model.nix
-      ../../function.nix
-
-      ../common/sharedOptions.nix
-      ../common/targetNode.nix
-      ../common/targetResource.nix
-    ];
-
-    acmeNodeIP = config.nodes.acme.networking.primaryIPAddress;
-
-    nodes =
-      {
-        deployer = {
-          imports = [ ../common/deployerNode.nix ];
-          _module.args = { inherit inputs sources; };
-          enableAcme = config.enableAcme;
-          acmeNodeIP = config.nodes.acme.networking.primaryIPAddress;
-        };
-      }
-
-      //
-
-        (
-          if config.enableAcme then
-            {
-              acme = {
-                ## FIXME: This makes `nodes.acme` into a local resolver. Maybe this will
-                ## break things once we play with DNS?
-                imports = [ "${inputs.nixpkgs}/nixos/tests/common/acme/server" ];
-                ## We aren't testing ACME - we just want certificates.
-                systemd.services.pebble.environment.PEBBLE_VA_ALWAYS_VALID = "1";
-              };
-            }
-          else
-            { }
-        )
-
-      //
-
-        genAttrs config.targetMachines (_: {
-          imports = [ ../common/targetNode.nix ];
-          _module.args = { inherit inputs sources; };
-          enableAcme = config.enableAcme;
-          acmeNodeIP = if config.enableAcme then config.nodes.acme.networking.primaryIPAddress else null;
-        });
-
-    testScript = ''
-      ${forConcat (attrNames config.nodes) (n: ''
-        ${n}.start()
-      '')}
-
-      ${forConcat (attrNames config.nodes) (n: ''
-        ${n}.wait_for_unit("multi-user.target")
-      '')}
-
-      ## A subset of the repository that is necessary for this test. It will be
-      ## copied inside the test. The smaller this set, the faster our CI, because we
-      ## won't need to re-run when things change outside of it.
-      with subtest("Unpacking"):
-        deployer.succeed("cp -r --no-preserve=mode ${
-          fileset.toSource {
-            root = ../../..;
-            fileset = config.sourceFileset;
-          }
-        }/* .")
-
-      with subtest("Configure the network"):
-        ${forConcat config.targetMachines (
-          tm:
-          let
-            targetNetworkJSON = writeText "target-network.json" (
-              toJSON config.nodes.${tm}.system.build.networkConfig
-            );
-          in
-          ''
-            deployer.copy_from_host("${targetNetworkJSON}", "${config.pathFromRoot}/${tm}-network.json")
-          ''
-        )}
-
-      with subtest("Configure the deployer key"):
-        deployer.succeed("""mkdir -p ~/.ssh && ssh-keygen -t rsa -N "" -f ~/.ssh/id_rsa""")
-        deployer_key = deployer.succeed("cat ~/.ssh/id_rsa.pub").strip()
-        ${forConcat config.targetMachines (tm: ''
-          ${tm}.succeed(f"mkdir -p /root/.ssh && echo '{deployer_key}' >> /root/.ssh/authorized_keys")
-        '')}
-
-      with subtest("Configure the target host key"):
-        ${forConcat config.targetMachines (tm: ''
-          host_key = ${tm}.succeed("ssh-keyscan ${tm} | grep -v '^#' | cut -f 2- -d ' ' | head -n 1")
-          deployer.succeed(f"echo '{host_key}' > ${config.pathFromRoot}/${tm}_host_key.pub")
-        '')}
-
-      # with subtest("Override the flake and its lock"):
-      #   deployer.succeed("cp ${config.pathFromRoot}/flake-under-test.nix flake.nix")
-
-      ${optionalString config.enableAcme ''
-        with subtest("Set up handmade DNS"):
-          deployer.succeed("echo '${config.nodes.acme.networking.primaryIPAddress}' > ${config.pathFromRoot}/acme_server_ip")
-      ''}
-
-      ${config.extraTestScript}
-    '';
-  };
-}
diff --git a/deployment/check/data-model/default.nix b/deployment/check/data-model/default.nix
index 5eafbbbc..11c1fb37 100644
--- a/deployment/check/data-model/default.nix
+++ b/deployment/check/data-model/default.nix
@@ -8,7 +8,7 @@ runNixOSTest {
   imports = [
     ../../data-model.nix
     ../../function.nix
-    ./common-nixosTest.nix
+    ../common/nixosTest.nix
     ./nixosTest.nix
   ];
   _module.args = { inherit inputs sources; };
diff --git a/deployment/check/panel/constants.nix b/deployment/check/panel/constants.nix
index ce3b5e4d..a48d9076 100644
--- a/deployment/check/panel/constants.nix
+++ b/deployment/check/panel/constants.nix
@@ -8,4 +8,5 @@
   pathToRoot = ../../..;
   pathFromRoot = ./.;
   enableAcme = true;
+  useFlake = true;
 }
diff --git a/deployment/check/panel/nixosTest.nix b/deployment/check/panel/nixosTest.nix
index ffcb8e53..fddad457 100644
--- a/deployment/check/panel/nixosTest.nix
+++ b/deployment/check/panel/nixosTest.nix
@@ -128,6 +128,7 @@ in
   sourceFileset = lib.fileset.unions [
     ./constants.nix
     ./deployment.nix
+    (config.pathToCwd + "/flake-under-test.nix")
 
     # REVIEW: I would like to be able to grab all of `/deployment` minus
     # `/deployment/check`, but I can't because there is a bunch of other files