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simple server client test
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olaf
fricklerhandwerk
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commit
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@ -260,157 +260,55 @@ result=$(readlink -f ./result) rm ./result && nix-store --delete $result
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## Tests that need multiple virtual machines
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Tests can involve multiple virtual machines.
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For example to test server client communication.
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This example uses the use-case of a [REST](https://en.m.wikipedia.org/wiki/REST) interface to a [PostgreSQL](https://www.postgresql.org/) database.
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The following example Nix expression is adapted from [How to use NixOS for lightweight integration tests](https://www.haskellforall.com/2020/11/how-to-use-nixos-for-lightweight.html).
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This tutorial follows [PostgREST tutorial](https://postgrest.org/en/stable/tutorials/tut0.html), a generic [RESTful API](https://restfulapi.net/) for PostgreSQL.
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If you skim over the official tutorial, you'll notice there's quite a bit of setup in order to test if all the steps work.
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The setup includes:
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- A virtual machine named `server` running PostgreSQL and PostgREST.
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- A virtual machine named `client` running HTTP client queries using `curl`.
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- A virtual machine named `server` running nginx.
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- A virtual machine named `client` performing a HTTP request.
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- A `testScript` orchestrating testing logic between `client` and `server`.
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The complete `postgrest.nix` file looks like the following:
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The test performs the folling steps:
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1) starts the server and waits for it to be ready.
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1) starts the client and waits for it to be ready.
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1) executes curl and uses grep to assess for the expected return string.
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the test passes or fails on the basis of grep's return value.
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The complete `server-client-test.nix` file content looks like the following:
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```{code-block}
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let
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# Pin Nixpkgs, as some packages are broken in the 22.11 release
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nixpkgs = fetchTarball "https://github.com/NixOS/nixpkgs/archive/0f8f64b54ed07966b83db2f20c888d5e035012ef.tar.gz";
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pkgs = import nixpkgs { config = {}; overlays = []; };
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# Single source of truth for all tutorial constants
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database = "postgres";
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schema = "api";
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table = "todos";
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username = "authenticator";
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password = "mysecretpassword";
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webRole = "web_anon";
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postgrestPort = 3000;
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# NixOS module shared between server and client
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sharedModule = {
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# Since it's common for CI not to have $DISPLAY available, explicitly disable graphics support
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virtualisation.graphics = false;
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};
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nixpkgs = fetchTarball "https://github.com/NixOS/nixpkgs/archive/nixpkgs-unstable.tar.gz";
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pkgs = import nixpkgs { };
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in
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pkgs.nixosTest {
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# NixOS tests are run inside a virtual machine, and here you specify its system type
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system = "x86_64-linux";
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name = "postgres-test";
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nodes = {
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server = { config, pkgs, ... }: {
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imports = [ sharedModule ];
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networking.firewall.allowedTCPPorts = [ postgrestPort ];
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services.postgresql = {
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enable = true;
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initialScript = pkgs.writeText "initialScript.sql" ''
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create schema ${schema};
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create table ${schema}.${table} (
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id serial primary key,
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done boolean not null default false,
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task text not null,
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due timestamptz
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);
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insert into ${schema}.${table} (task) values ('finish tutorial 0'), ('pat self on back');
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create role ${webRole} nologin;
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grant usage on schema ${schema} to ${webRole};
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grant select on ${schema}.${table} to ${webRole};
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create role ${username} inherit login password '${password}';
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grant ${webRole} to ${username};
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'';
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};
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users = {
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mutableUsers = false;
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users = {
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# For ease of debugging the VM as the `root` user
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root.password = "";
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# Create a system user that matches the database user so that you
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# can use peer authentication. The tutorial defines a password,
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# but it's not necessary.
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"${username}".isSystemUser = true;
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};
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};
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systemd.services.postgrest = {
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wantedBy = [ "multi-user.target" ];
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after = [ "postgresql.service" ];
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script =
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let
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configuration = pkgs.writeText "tutorial.conf" ''
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db-uri = "postgres://${username}:${password}@localhost:${toString config.services.postgresql.port}/${database}"
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db-schema = "${schema}"
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db-anon-role = "${username}"
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'';
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in "${pkgs.haskellPackages.postgrest}/bin/postgrest ${configuration}";
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serviceConfig.User = username;
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pkgs.testers.runNixOSTest ({ lib, ... }: {
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name = "server-client-test";
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nodes.server = { pkgs, ... }: {
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networking = {
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firewall = {
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allowedTCPPorts = [ 80 ];
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};
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};
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client = {
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imports = [ sharedModule ];
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services.nginx = {
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enable = true;
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virtualHosts."server" = {
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#root = "/var/www/";
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};
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};
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};
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# Disable linting for simpler debugging of the testScript
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skipLint = true;
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nodes.client = { pkgs, ... }: {
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environment.systemPackages = with pkgs; [
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curl
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];
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};
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testScript = ''
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import json
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import sys
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start_all()
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server.wait_for_open_port(${toString postgrestPort})
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expected = [
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{"id": 1, "done": False, "task": "finish tutorial 0", "due": None},
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{"id": 2, "done": False, "task": "pat self on back", "due": None},
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]
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actual = json.loads(
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client.succeed(
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"${pkgs.curl}/bin/curl http://server:${toString postgrestPort}/${table}"
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)
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)
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assert expected == actual, "table query returns expected content"
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server.wait_for_unit("default.target")
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client.wait_for_unit("default.target")
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client.succeed("curl http://server/ |grep -o \"Welcome to nginx!\"")
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'';
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}
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})
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```
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Unlike the previous example, the virtual machines need an expressive name to distinguish them.
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For this example we choose `client` and `server`.
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Set up all machines and run the test script:
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```shell-session
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nix-build postgrest.nix
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```
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...
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test script finished in 10.96s
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cleaning up
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killing client (pid 10)
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killing server (pid 22)
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(0.00 seconds)
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/nix/store/bx7z3imvxxpwkkza10vb23czhw7873w2-vm-test-run-unnamed
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```
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## Additional information regarding NixOS tests:
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- Running integration tests on CI requires hardware acceleration, which many CIs do not support.
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