manual: re-add running nixos tests sections

nixos/doc/manual/development/development.xml

···
 <xi:include href="writing-modules.xml" />
 <xi:include href="building-parts.xml" />
 <xi:include href="building-nixos.xml" />
+<xi:include href="nixos-tests.xml" />
 <xi:include href="testing-installer.xml" />
 
 </part>

nixos/doc/manual/development/nixos-tests.xml

···
 
 <xi:include href="writing-nixos-tests.xml" />
 <xi:include href="running-nixos-tests.xml" />
+<xi:include href="running-nixos-tests-interactively.xml" />
 
-</chapter>
+</chapter>

nixos/doc/manual/development/running-nixos-tests-interactively.xml

···
+<section xmlns="http://docbook.org/ns/docbook"
+        xmlns:xlink="http://www.w3.org/1999/xlink"
+        xmlns:xi="http://www.w3.org/2001/XInclude"
+        version="5.0"
+        xml:id="sec-running-nixos-tests">
+<title>Running Tests interactively</title>
+
+<para>The test itself can be run interactively.  This is
+particularly useful when developing or debugging a test:
+
+<screen>
+$ nix-build nixos/tests/login.nix -A driver
+$ ./result/bin/nixos-test-driver
+starting VDE switch for network 1
+&gt;
+</screen>
+
+You can then take any Perl statement, e.g.
+
+<screen>
+&gt; startAll
+&gt; testScript
+&gt; $machine->succeed("touch /tmp/foo")
+</screen>
+
+The function <command>testScript</command> executes the entire test
+script and drops you back into the test driver command line upon its
+completion.  This allows you to inspect the state of the VMs after the
+test (e.g. to debug the test script).</para>
+
+<para>To just start and experiment with the VMs, run:
+
+<screen>
+$ nix-build nixos/tests/login.nix -A driver
+$ ./result/bin/nixos-run-vms
+</screen>
+
+The script <command>nixos-run-vms</command> starts the virtual
+machines defined by test.  The root file system of the VMs is created
+on the fly and kept across VM restarts in
+<filename>./</filename><varname>hostname</varname><filename>.qcow2</filename>.</para>
+
+</section>

nixos/doc/manual/development/running-nixos-tests.xml

···
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
-        xml:id="sec-running-nixos-tests">
+        xml:id="sec-running-nixos-tests-interactively">
 
 <title>Running Tests</title>
 
···
 </screen>
 
 </para>
-
-<title>Running Tests interactively</title>
-
-<para>The test itself can be run interactively.  This is
-particularly useful when developing or debugging a test:
-
-<screen>
-$ nix-build nixos/tests/login.nix -A driver
-$ ./result/bin/nixos-test-driver
-starting VDE switch for network 1
-&gt;
-</screen>
-
-You can then take any Perl statement, e.g.
-
-<screen>
-&gt; startAll
-&gt; testScript
-&gt; $machine->succeed("touch /tmp/foo")
-</screen>
-
-The function <command>testScript</command> executes the entire test
-script and drops you back into the test driver command line upon its
-completion.  This allows you to inspect the state of the VMs after the
-test (e.g. to debug the test script).</para>
-
-<para>To just start and experiment with the VMs, run:
-
-<screen>
-$ nix-build nixos/tests/login.nix -A driver
-$ ./result/bin/nixos-run-vms
-</screen>
-
-The script <command>nixos-run-vms</command> starts the virtual
-machines defined by test.  The root file system of the VMs is created
-on the fly and kept across VM restarts in
-<filename>./</filename><varname>hostname</varname><filename>.qcow2</filename>.</para>
-
 </section>