diff --git a/tests/default.nix b/tests/default.nix
index b29b27ac..9eb5afcd 100644
--- a/tests/default.nix
+++ b/tests/default.nix
@@ -14,7 +14,15 @@ let
   modules = import ../modules/modules.nix {
     inherit lib pkgs;
     check = false;
-  };
+  } ++ [
+    # Fix impurities. Without these some of the user's environment
+    # will leak into the tests through `builtins.getEnv`.
+    {
+      xdg.enable = true;
+      home.username = "hm-user";
+      home.homeDirectory = "/home/hm-user";
+    }
+  ];
 
 in
 
diff --git a/tests/modules/home-environment/session-variables-expected.txt b/tests/modules/home-environment/session-variables-expected.txt
index 5c3868c3..4e18e2b3 100644
--- a/tests/modules/home-environment/session-variables-expected.txt
+++ b/tests/modules/home-environment/session-variables-expected.txt
@@ -4,3 +4,6 @@ export __HM_SESS_VARS_SOURCED=1
 
 export V1="v1"
 export V2="v2-v1"
+export XDG_CACHE_HOME="/home/hm-user/.cache"
+export XDG_CONFIG_HOME="/home/hm-user/.config"
+export XDG_DATA_HOME="/home/hm-user/.local/share"
diff --git a/tests/modules/misc/xsession/basic-xprofile-expected.txt b/tests/modules/misc/xsession/basic-xprofile-expected.txt
index 05733a97..282f8f5c 100644
--- a/tests/modules/misc/xsession/basic-xprofile-expected.txt
+++ b/tests/modules/misc/xsession/basic-xprofile-expected.txt
@@ -1,4 +1,4 @@
-. "/test-home/.nix-profile/etc/profile.d/hm-session-vars.sh"
+. "/home/hm-user/.nix-profile/etc/profile.d/hm-session-vars.sh"
 
 if [ -e "$HOME/.profile" ]; then
   . "$HOME/.profile"
diff --git a/tests/modules/misc/xsession/basic.nix b/tests/modules/misc/xsession/basic.nix
index 39df6362..d6756291 100644
--- a/tests/modules/misc/xsession/basic.nix
+++ b/tests/modules/misc/xsession/basic.nix
@@ -4,8 +4,6 @@ with lib;
 
 {
   config = {
-    home.homeDirectory = "/test-home";
-
     xsession = {
       enable = true;
       windowManager.command = "window manager command";
diff --git a/tests/modules/misc/xsession/keyboard-without-layout.nix b/tests/modules/misc/xsession/keyboard-without-layout.nix
index 015efe61..90038cfd 100644
--- a/tests/modules/misc/xsession/keyboard-without-layout.nix
+++ b/tests/modules/misc/xsession/keyboard-without-layout.nix
@@ -6,8 +6,6 @@ with lib;
   config = {
     home.stateVersion = "19.09";
 
-    home.homeDirectory = "/test-home";
-
     home.keyboard = { options = [ "ctrl:nocaps" "altwin:no_win" ]; };
 
     xsession = {
diff --git a/tests/modules/programs/bash/session-variables-expected.txt b/tests/modules/programs/bash/session-variables-expected.txt
index e13d63d4..0d93217a 100644
--- a/tests/modules/programs/bash/session-variables-expected.txt
+++ b/tests/modules/programs/bash/session-variables-expected.txt
@@ -1,6 +1,6 @@
 # -*- mode: sh -*-
 
-. "/home/testuser/.nix-profile/etc/profile.d/hm-session-vars.sh"
+. "/home/hm-user/.nix-profile/etc/profile.d/hm-session-vars.sh"
 
 export V1="v1"
 export V2="v2-v1"
diff --git a/tests/modules/programs/bash/session-variables.nix b/tests/modules/programs/bash/session-variables.nix
index ea789a1d..1ef65a34 100644
--- a/tests/modules/programs/bash/session-variables.nix
+++ b/tests/modules/programs/bash/session-variables.nix
@@ -13,8 +13,6 @@ with lib;
       };
     };
 
-    home.homeDirectory = "/home/testuser";
-
     nmt.script = ''
       assertFileExists home-files/.profile
       assertFileContent \
diff --git a/tests/modules/programs/getmail/getmail.nix b/tests/modules/programs/getmail/getmail.nix
index fe10b98f..b0d979c4 100644
--- a/tests/modules/programs/getmail/getmail.nix
+++ b/tests/modules/programs/getmail/getmail.nix
@@ -6,9 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-
     accounts.email.accounts = {
       "hm@example.com" = {
         getmail = {
diff --git a/tests/modules/programs/lieer/lieer.nix b/tests/modules/programs/lieer/lieer.nix
index 1671f4f5..2ce4fb4e 100644
--- a/tests/modules/programs/lieer/lieer.nix
+++ b/tests/modules/programs/lieer/lieer.nix
@@ -6,9 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-
     programs.lieer.enable = true;
 
     accounts.email.accounts = { "hm@example.com".lieer.enable = true; };
diff --git a/tests/modules/programs/mbsync/mbsync.nix b/tests/modules/programs/mbsync/mbsync.nix
index 03a54c17..fa8e28cb 100644
--- a/tests/modules/programs/mbsync/mbsync.nix
+++ b/tests/modules/programs/mbsync/mbsync.nix
@@ -6,9 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-
     programs.mbsync = {
       enable = true;
       groups.inboxes = {
diff --git a/tests/modules/programs/neomutt/neomutt-with-msmtp.nix b/tests/modules/programs/neomutt/neomutt-with-msmtp.nix
index 5f94d21a..22f65599 100644
--- a/tests/modules/programs/neomutt/neomutt-with-msmtp.nix
+++ b/tests/modules/programs/neomutt/neomutt-with-msmtp.nix
@@ -6,11 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-    xdg.configHome = mkForce "/home/hm-user/.config";
-    xdg.cacheHome = mkForce "/home/hm-user/.cache";
-
     accounts.email.accounts = {
       "hm@example.com" = {
         primary = true;
diff --git a/tests/modules/programs/neomutt/neomutt.nix b/tests/modules/programs/neomutt/neomutt.nix
index 91cb9dca..c0caa44a 100644
--- a/tests/modules/programs/neomutt/neomutt.nix
+++ b/tests/modules/programs/neomutt/neomutt.nix
@@ -6,11 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-    xdg.configHome = mkForce "/home/hm-user/.config";
-    xdg.cacheHome = mkForce "/home/hm-user/.cache";
-
     accounts.email.accounts = {
       "hm@example.com" = {
         primary = true;
diff --git a/tests/modules/programs/tmux/hm-session-vars.sh b/tests/modules/programs/tmux/hm-session-vars.sh
deleted file mode 100644
index 40d9c24b..00000000
--- a/tests/modules/programs/tmux/hm-session-vars.sh
+++ /dev/null
@@ -1,5 +0,0 @@
-# Only source this once.
-if [ -n "$__HM_SESS_VARS_SOURCED" ]; then return; fi
-export __HM_SESS_VARS_SOURCED=1
-
-export TMUX_TMPDIR="${XDG_RUNTIME_DIR:-"/run/user/\$(id -u)"}"
diff --git a/tests/modules/programs/tmux/secure-socket-enabled.nix b/tests/modules/programs/tmux/secure-socket-enabled.nix
index 7e8c535c..ca2de663 100644
--- a/tests/modules/programs/tmux/secure-socket-enabled.nix
+++ b/tests/modules/programs/tmux/secure-socket-enabled.nix
@@ -11,9 +11,8 @@ with lib;
 
     nmt.script = ''
       assertFileExists home-path/etc/profile.d/hm-session-vars.sh
-      assertFileContent home-path/etc/profile.d/hm-session-vars.sh ${
-        ./hm-session-vars.sh
-      }
+      assertFileContains home-path/etc/profile.d/hm-session-vars.sh \
+        'export TMUX_TMPDIR="''${XDG_RUNTIME_DIR:-"/run/user/\$(id -u)"}"'
     '';
   };
 }
diff --git a/tests/modules/services/lieer/lieer-service.nix b/tests/modules/services/lieer/lieer-service.nix
index faef5053..03dcdc74 100644
--- a/tests/modules/services/lieer/lieer-service.nix
+++ b/tests/modules/services/lieer/lieer-service.nix
@@ -6,9 +6,6 @@ with lib;
   imports = [ ../../accounts/email-test-accounts.nix ];
 
   config = {
-    home.username = "hm-user";
-    home.homeDirectory = "/home/hm-user";
-
     services.lieer.enable = true;
 
     accounts.email.accounts = {
diff --git a/tests/modules/targets/generic-linux-session-vars-expected.txt b/tests/modules/targets/generic-linux-session-vars-expected.txt
deleted file mode 100644
index ad9e0ada..00000000
--- a/tests/modules/targets/generic-linux-session-vars-expected.txt
+++ /dev/null
@@ -1,6 +0,0 @@
-# Only source this once.
-if [ -n "$__HM_SESS_VARS_SOURCED" ]; then return; fi
-export __HM_SESS_VARS_SOURCED=1
-
-export XDG_DATA_DIRS="/nix/var/nix/profiles/default/share:/homeless-shelter/.nix-profile/share${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"
-. "@nix@/etc/profile.d/nix.sh"
diff --git a/tests/modules/targets/generic-linux.nix b/tests/modules/targets/generic-linux.nix
index 2e06b254..8596ac3d 100644
--- a/tests/modules/targets/generic-linux.nix
+++ b/tests/modules/targets/generic-linux.nix
@@ -4,20 +4,16 @@ with lib;
 
 {
   config = {
-    home.homeDirectory = "/homeless-shelter";
-
     targets.genericLinux.enable = true;
 
     nmt.script = ''
       assertFileExists home-path/etc/profile.d/hm-session-vars.sh
-      assertFileContent \
+      assertFileContains \
         home-path/etc/profile.d/hm-session-vars.sh \
-        ${
-          pkgs.substituteAll {
-            src = ./generic-linux-session-vars-expected.txt;
-            nix = pkgs.nix;
-          }
-        }
+        'export XDG_DATA_DIRS="/nix/var/nix/profiles/default/share:/home/hm-user/.nix-profile/share''${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"'
+      assertFileContains \
+        home-path/etc/profile.d/hm-session-vars.sh \
+        '. "${pkgs.nix}/etc/profile.d/nix.sh"'
     '';
   };
 }