diff --git a/tests/github-flakes.nix b/tests/github-flakes.nix
index a47610d9a..2de3e2bc0 100644
--- a/tests/github-flakes.nix
+++ b/tests/github-flakes.nix
@@ -1,6 +1,6 @@
 { nixpkgs, system, overlay }:
 
-with import (nixpkgs + "/nixos/lib/testing.nix") {
+with import (nixpkgs + "/nixos/lib/testing-python.nix") {
   inherit system;
   extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
 };
@@ -113,36 +113,37 @@ makeTest (
         };
     };
 
-  testScript = { nodes }:
-    ''
-      use POSIX qw(strftime);
+  testScript = { nodes }: ''
+    # fmt: off
+    import json
+    import time
 
-      startAll;
+    start_all()
 
-      $github->waitForUnit("httpd.service");
+    github.wait_for_unit("httpd.service")
 
-      $client->succeed("curl -v https://github.com/ >&2");
+    client.succeed("curl -v https://github.com/ >&2")
+    client.succeed("nix registry list | grep nixpkgs")
 
-      $client->succeed("nix registry list | grep nixpkgs");
+    rev = client.succeed("nix flake info nixpkgs --json | jq -r .revision")
+    assert rev.strip() == "${nixpkgs.rev}", "revision mismatch"
 
-      $client->succeed("nix flake info nixpkgs --json | jq -r .revision") eq "${nixpkgs.rev}\n"
-        or die "revision mismatch";
+    client.succeed("nix registry pin nixpkgs")
 
-      $client->succeed("nix registry pin nixpkgs");
+    client.succeed("nix flake info nixpkgs --tarball-ttl 0 >&2")
 
-      $client->succeed("nix flake info nixpkgs --tarball-ttl 0 >&2");
+    # Shut down the web server. The flake should be cached on the client.
+    github.succeed("systemctl stop httpd.service")
 
-      # Shut down the web server. The flake should be cached on the client.
-      $github->succeed("systemctl stop httpd.service");
+    info = json.loads(client.succeed("nix flake info nixpkgs --json"))
+    date = time.strftime("%Y%m%d%H%M%S", time.gmtime(info['lastModified']))
+    assert date == "${nixpkgs.lastModifiedDate}", "time mismatch"
 
-      my $date = $client->succeed("nix flake info nixpkgs --json | jq -M .lastModified");
-      strftime("%Y%m%d%H%M%S", gmtime($date)) eq "${nixpkgs.lastModifiedDate}" or die "time mismatch";
+    client.succeed("nix build nixpkgs#hello")
 
-      $client->succeed("nix build nixpkgs#hello");
-
-      # The build shouldn't fail even with --tarball-ttl 0 (the server
-      # being down should not be a fatal error).
-      $client->succeed("nix build nixpkgs#fuse --tarball-ttl 0");
-    '';
+    # The build shouldn't fail even with --tarball-ttl 0 (the server
+    # being down should not be a fatal error).
+    client.succeed("nix build nixpkgs#fuse --tarball-ttl 0")
+  '';
 
 })
diff --git a/tests/nix-copy-closure.nix b/tests/nix-copy-closure.nix
index 9c9d119b7..68f9c70b3 100644
--- a/tests/nix-copy-closure.nix
+++ b/tests/nix-copy-closure.nix
@@ -2,7 +2,7 @@
 
 { nixpkgs, system, overlay }:
 
-with import (nixpkgs + "/nixos/lib/testing.nix") {
+with import (nixpkgs + "/nixos/lib/testing-python.nix") {
   inherit system;
   extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
 };
@@ -25,41 +25,46 @@ makeTest (let pkgA = pkgs.cowsay; pkgB = pkgs.wget; pkgC = pkgs.hello; in {
         };
     };
 
-  testScript = { nodes }:
-    ''
-      startAll;
+  testScript = { nodes }: ''
+    # fmt: off
+    import subprocess
 
-      # Create an SSH key on the client.
-      my $key = `${pkgs.openssh}/bin/ssh-keygen -t ed25519 -f key -N ""`;
-      $client->succeed("mkdir -m 700 /root/.ssh");
-      $client->copyFileFromHost("key", "/root/.ssh/id_ed25519");
-      $client->succeed("chmod 600 /root/.ssh/id_ed25519");
+    start_all()
 
-      # Install the SSH key on the server.
-      $server->succeed("mkdir -m 700 /root/.ssh");
-      $server->copyFileFromHost("key.pub", "/root/.ssh/authorized_keys");
-      $server->waitForUnit("sshd");
-      $client->waitForUnit("network.target");
-      $client->succeed("ssh -o StrictHostKeyChecking=no " . $server->name() . " 'echo hello world'");
+    # Create an SSH key on the client.
+    subprocess.run([
+      "${pkgs.openssh}/bin/ssh-keygen", "-t", "ed25519", "-f", "key", "-N", ""
+    ], capture_output=True, check=True)
 
-      # Copy the closure of package A from the client to the server.
-      $server->fail("nix-store --check-validity ${pkgA}");
-      $client->succeed("nix-copy-closure --to server --gzip ${pkgA} >&2");
-      $server->succeed("nix-store --check-validity ${pkgA}");
+    client.succeed("mkdir -m 700 /root/.ssh")
+    client.copy_from_host("key", "/root/.ssh/id_ed25519")
+    client.succeed("chmod 600 /root/.ssh/id_ed25519")
 
-      # Copy the closure of package B from the server to the client.
-      $client->fail("nix-store --check-validity ${pkgB}");
-      $client->succeed("nix-copy-closure --from server --gzip ${pkgB} >&2");
-      $client->succeed("nix-store --check-validity ${pkgB}");
+    # Install the SSH key on the server.
+    server.succeed("mkdir -m 700 /root/.ssh")
+    server.copy_from_host("key.pub", "/root/.ssh/authorized_keys")
+    server.wait_for_unit("sshd")
+    client.wait_for_unit("network.target")
+    client.succeed(f"ssh -o StrictHostKeyChecking=no {server.name} 'echo hello world'")
 
-      # Copy the closure of package C via the SSH substituter.
-      $client->fail("nix-store -r ${pkgC}");
-      # FIXME
-      #$client->succeed(
-      #  "nix-store --option use-ssh-substituter true"
-      #  . " --option ssh-substituter-hosts root\@server"
-      #  . " -r ${pkgC} >&2");
-      #$client->succeed("nix-store --check-validity ${pkgC}");
-    '';
+    # Copy the closure of package A from the client to the server.
+    server.fail("nix-store --check-validity ${pkgA}")
+    client.succeed("nix-copy-closure --to server --gzip ${pkgA} >&2")
+    server.succeed("nix-store --check-validity ${pkgA}")
 
+    # Copy the closure of package B from the server to the client.
+    client.fail("nix-store --check-validity ${pkgB}")
+    client.succeed("nix-copy-closure --from server --gzip ${pkgB} >&2")
+    client.succeed("nix-store --check-validity ${pkgB}")
+
+    # Copy the closure of package C via the SSH substituter.
+    client.fail("nix-store -r ${pkgC}")
+    # FIXME
+    # client.succeed(
+    #   "nix-store --option use-ssh-substituter true"
+    #   " --option ssh-substituter-hosts root\@server"
+    #   " -r ${pkgC} >&2"
+    # )
+    # client.succeed("nix-store --check-validity ${pkgC}")
+  '';
 })
diff --git a/tests/remote-builds.nix b/tests/remote-builds.nix
index 153956619..305c82394 100644
--- a/tests/remote-builds.nix
+++ b/tests/remote-builds.nix
@@ -2,7 +2,7 @@
 
 { nixpkgs, system, overlay }:
 
-with import (nixpkgs + "/nixos/lib/testing.nix") {
+with import (nixpkgs + "/nixos/lib/testing-python.nix") {
   inherit system;
   extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
 };
@@ -66,44 +66,46 @@ in
         };
     };
 
-  testScript = { nodes }:
-    ''
-      startAll;
+  testScript = { nodes }: ''
+    # fmt: off
+    import subprocess
 
-      # Create an SSH key on the client.
-      my $key = `${pkgs.openssh}/bin/ssh-keygen -t ed25519 -f key -N ""`;
-      $client->succeed("mkdir -p -m 700 /root/.ssh");
-      $client->copyFileFromHost("key", "/root/.ssh/id_ed25519");
-      $client->succeed("chmod 600 /root/.ssh/id_ed25519");
+    start_all()
 
-      # Install the SSH key on the builders.
-      $client->waitForUnit("network.target");
-      foreach my $builder ($builder1, $builder2) {
-          $builder->succeed("mkdir -p -m 700 /root/.ssh");
-          $builder->copyFileFromHost("key.pub", "/root/.ssh/authorized_keys");
-          $builder->waitForUnit("sshd");
-          $client->succeed("ssh -o StrictHostKeyChecking=no " . $builder->name() . " 'echo hello world'");
-      }
+    # Create an SSH key on the client.
+    subprocess.run([
+      "${pkgs.openssh}/bin/ssh-keygen", "-t", "ed25519", "-f", "key", "-N", ""
+    ], capture_output=True, check=True)
+    client.succeed("mkdir -p -m 700 /root/.ssh")
+    client.copy_from_host("key", "/root/.ssh/id_ed25519")
+    client.succeed("chmod 600 /root/.ssh/id_ed25519")
 
-      # Perform a build and check that it was performed on the builder.
-      my $out = $client->succeed(
-        "nix-build ${expr nodes.client.config 1} 2> build-output",
-        "grep -q Hello build-output"
-      );
-      $builder1->succeed("test -e $out");
+    # Install the SSH key on the builders.
+    client.wait_for_unit("network.target")
+    for builder in [builder1, builder2]:
+      builder.succeed("mkdir -p -m 700 /root/.ssh")
+      builder.copy_from_host("key.pub", "/root/.ssh/authorized_keys")
+      builder.wait_for_unit("sshd")
+      client.succeed(f"ssh -o StrictHostKeyChecking=no {builder.name} 'echo hello world'")
 
-      # And a parallel build.
-      my ($out1, $out2) = split /\s/,
-          $client->succeed('nix-store -r $(nix-instantiate ${expr nodes.client.config 2})\!out $(nix-instantiate ${expr nodes.client.config 3})\!out');
-      $builder1->succeed("test -e $out1 -o -e $out2");
-      $builder2->succeed("test -e $out1 -o -e $out2");
+    # Perform a build and check that it was performed on the builder.
+    out = client.succeed(
+      "nix-build ${expr nodes.client.config 1} 2> build-output",
+      "grep -q Hello build-output"
+    )
+    builder1.succeed(f"test -e {out}")
 
-      # And a failing build.
-      $client->fail("nix-build ${expr nodes.client.config 5}");
+    # And a parallel build.
+    paths = client.succeed(r'nix-store -r $(nix-instantiate ${expr nodes.client.config 2})\!out $(nix-instantiate ${expr nodes.client.config 3})\!out')
+    out1, out2 = paths.split()
+    builder1.succeed(f"test -e {out1} -o -e {out2}")
+    builder2.succeed(f"test -e {out1} -o -e {out2}")
 
-      # Test whether the build hook automatically skips unavailable builders.
-      $builder1->block;
-      $client->succeed("nix-build ${expr nodes.client.config 4}");
-    '';
+    # And a failing build.
+    client.fail("nix-build ${expr nodes.client.config 5}")
 
+    # Test whether the build hook automatically skips unavailable builders.
+    builder1.block()
+    client.succeed("nix-build ${expr nodes.client.config 4}")
+  '';
 })
diff --git a/tests/setuid.nix b/tests/setuid.nix
index 6f2f7d392..8d31a18be 100644
--- a/tests/setuid.nix
+++ b/tests/setuid.nix
@@ -2,7 +2,7 @@
 
 { nixpkgs, system, overlay }:
 
-with import (nixpkgs + "/nixos/lib/testing.nix") {
+with import (nixpkgs + "/nixos/lib/testing-python.nix") {
   inherit system;
   extraConfigurations = [ { nixpkgs.overlays = [ overlay ]; } ];
 };
@@ -17,94 +17,109 @@ makeTest {
       virtualisation.pathsInNixDB = [ pkgs.stdenv pkgs.pkgsi686Linux.stdenv ];
     };
 
-  testScript = { nodes }:
-    ''
-      startAll;
+  testScript = { nodes }: ''
+    # fmt: off
+    start_all()
 
-      # Copying to /tmp should succeed.
-      $machine->succeed('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-      ")\' ');
+    # Copying to /tmp should succeed.
+    machine.succeed(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      # Creating a setuid binary should fail.
-      $machine->fail('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        chmod 4755 /tmp/id
-      ")\' ');
+    # Creating a setuid binary should fail.
+    machine.fail(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      chmod 4755 /tmp/id
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      # Creating a setgid binary should fail.
-      $machine->fail('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" {} "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        chmod 2755 /tmp/id
-      ")\' ');
+    # Creating a setgid binary should fail.
+    machine.fail(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" {} "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      chmod 2755 /tmp/id
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      # The checks should also work on 32-bit binaries.
-      $machine->fail('nix-build --no-sandbox -E \'(with import <nixpkgs> { system = "i686-linux"; }; runCommand "foo" {} "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        chmod 2755 /tmp/id
-      ")\' ');
+    # The checks should also work on 32-bit binaries.
+    machine.fail(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> { system = "i686-linux"; }; runCommand "foo" {} "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      chmod 2755 /tmp/id
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      # The tests above use fchmodat(). Test chmod() as well.
-      $machine->succeed('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        perl -e \"chmod 0666, qw(/tmp/id) or die\"
-      ")\' ');
+    # The tests above use fchmodat(). Test chmod() as well.
+    machine.succeed(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      perl -e \"chmod 0666, qw(/tmp/id) or die\"
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 666 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 666 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      $machine->fail('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        perl -e \"chmod 04755, qw(/tmp/id) or die\"
-      ")\' ');
+    machine.fail(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      perl -e \"chmod 04755, qw(/tmp/id) or die\"
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      # And test fchmod().
-      $machine->succeed('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 01750, \\\$x or die\"
-      ")\' ');
+    # And test fchmod().
+    machine.succeed(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 01750, \\\$x or die\"
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 1750 ]]');
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 1750 ]]')
 
-      $machine->succeed("rm /tmp/id");
+    machine.succeed("rm /tmp/id")
 
-      $machine->fail('nix-build --no-sandbox -E \'(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
-        mkdir -p $out
-        cp ${pkgs.coreutils}/bin/id /tmp/id
-        perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 04777, \\\$x or die\"
-      ")\' ');
+    machine.fail(r"""
+    nix-build --no-sandbox -E '(with import <nixpkgs> {}; runCommand "foo" { buildInputs = [ perl ]; } "
+      mkdir -p $out
+      cp ${pkgs.coreutils}/bin/id /tmp/id
+      perl -e \"my \\\$x; open \\\$x, qw(/tmp/id); chmod 04777, \\\$x or die\"
+    ")'
+    """.strip())
 
-      $machine->succeed('[[ $(stat -c %a /tmp/id) = 555 ]]');
-
-      $machine->succeed("rm /tmp/id");
-    '';
+    machine.succeed('[[ $(stat -c %a /tmp/id) = 555 ]]')
 
+    machine.succeed("rm /tmp/id")
+  '';
 }