Make it pass a minimal test

nixos/modules/services/monitoring/prometheus/alertmanager.nix

@@ -137,8 +137,7 @@ let
         '';
       };
     };
-    mkAMConfig = amCfg: amVersion:
+    mkAMConfig = amCfg: amVersion: [
-      config = mkMerge [
       (mkIf amCfg.enable {
         assertions = singleton {
           assertion = amCfg.configuration != null || amCfg.configText != null;
@@ -173,8 +172,5 @@ in {
     services.prometheus2.alertmanager = amOptions;
   };
 
-  config = mkMerge [
+  config = mkMerge ((mkAMConfig cfg "") ++ (mkAMConfig cfg2 "2"));
-    (mkAMConfig cfg "")
-    (mkAMConfig cfg2 "2")
-  ];
 }

nixos/modules/services/monitoring/prometheus/default.nix

@@ -22,7 +22,9 @@ let
 
   # a wrapper that verifies that the configuration is valid for
   # prometheus 2
-  prom2toolCheck = what: name: file: pkgs.runCommand "${name}-${what}-checked"
+  prom2toolCheck = what: name: file:
+    pkgs.runCommand
+      "${name}-${replaceStrings [" "] [""] what}-checked"
       { buildInputs = [ cfg2.package ]; } ''
     ln -s ${file} $out
     promtool ${what} $out
@@ -64,7 +66,7 @@ let
   # This becomes the main config file for Prometheus 2
   promConfig2 = {
     global = cfg2.globalConfig;
-    rule_files = map (prom2toolCheck "check-rules" "rules") (cfg2.ruleFiles ++ [
+    rule_files = map (prom2toolCheck "check rules" "rules") (cfg2.ruleFiles ++ [
       (pkgs.writeText "prometheus.rules" (concatStringsSep "\n" cfg2.rules))
     ]);
     scrape_configs = cfg2.scrapeConfigs;
@@ -83,7 +85,7 @@ let
     yml = if cfg2.configText != null then
       pkgs.writeText "prometheus.yml" cfg2.configText
       else generatedPrometheus2Yml;
-    in promtoo2lCheck "check-config" "prometheus.yml" yml;
+    in prom2toolCheck "check config" "prometheus.yml" yml;
 
   cmdlineArgs2 = cfg2.extraFlags ++ [
     "--storage.tsdb.path=${cfg2.dataDir}/data/"
@@ -704,7 +706,7 @@ in {
         after    = [ "network.target" ];
         script = ''
           #!/bin/sh
-          exec ${cfg.package}/bin/prometheus \
+          exec ${cfg2.package}/bin/prometheus \
             ${concatStringsSep " \\\n  " cmdlineArgs2}
         '';
         serviceConfig = {

nixos/tests/prometheus-2.nix

@@ -0,0 +1,34 @@
+import ./make-test.nix {
+  name = "prometheus-2";
+
+  nodes = {
+    one = { pkgs, ... }: {
+      services.prometheus2 = {
+        enable = true;
+        scrapeConfigs = [{
+          job_name = "prometheus";
+          static_configs = [{
+            targets = [ "127.0.0.1:9090" ];
+            labels = { instance = "localhost"; };
+          }];
+        }];
+        rules = [
+          ''
+            groups:
+              - name: test
+                rules:
+                  - record: testrule
+                    expr: count(up{job="prometheus"})
+          ''
+        ];
+      };
+    };
+  };
+
+  testScript = ''
+    startAll;
+    $one->waitForUnit("prometheus2.service");
+    $one->waitForOpenPort(9090);
+    $one->succeed("curl -s http://127.0.0.1:9090/metrics");
+  '';
+}