diff --git a/src/lib/Hydra/Controller/Project.pm b/src/lib/Hydra/Controller/Project.pm
index c7e64544..ed3c527c 100644
--- a/src/lib/Hydra/Controller/Project.pm
+++ b/src/lib/Hydra/Controller/Project.pm
@@ -162,6 +162,8 @@ sub updateProject {
         , declvalue => trim($c->stash->{params}->{declarative}->{value})
         });
     if (length($project->declfile)) {
+        # This logic also exists in the DeclarativeJobets tests.
+        # TODO: refactor and deduplicate.
         $project->jobsets->update_or_create(
             { name=> ".jobsets"
             , nixexprinput => ""
diff --git a/t/Hydra/Plugin/DeclarativeJobsets/basic.t b/t/Hydra/Plugin/DeclarativeJobsets/basic.t
new file mode 100644
index 00000000..ed91907c
--- /dev/null
+++ b/t/Hydra/Plugin/DeclarativeJobsets/basic.t
@@ -0,0 +1,63 @@
+use feature 'unicode_strings';
+use strict;
+use warnings;
+use Test2::V0;
+use Setup;
+
+my $ctx = test_context();
+my $db = $ctx->db;
+
+my $project = $db->resultset('Projects')->create({
+    name => "tests",
+    displayname => "",
+    owner => "root",
+    declfile => "declarative/project.json",
+    decltype => "path",
+    declvalue => $ctx->jobsdir,
+});
+
+subtest "Evaluating and building the top .jobsets jobset" => sub {
+    # This logic lives in the Project controller.
+    # Not great to duplicate it here.
+    # TODO: refactor and deduplicate.
+    my $jobset = $project->jobsets->create({
+        name=> ".jobsets",
+        nixexprinput => "",
+        nixexprpath => "",
+        emailoverride => "",
+        triggertime => time,
+    });
+
+    ok(evalSucceeds($jobset), "Evaluating the declarative jobsets with return code 0");
+    is(nrQueuedBuildsForJobset($jobset), 1, "We should have exactly 1 build queued, to build the jobsets data");
+
+    (my $build) = queuedBuildsForJobset($jobset);
+
+    is($build->job, "jobsets", "The only job should be jobsets");
+    ok(runBuild($build), "Build should exit with return code 0");
+    my $newbuild = $db->resultset('Builds')->find($build->id);
+    is($newbuild->finished, 1, "Build should be finished.");
+    is($newbuild->buildstatus, 0, "Build should have buildstatus 0.");
+
+    ok(sendNotifications(), "Notifications execute successfully.");
+};
+
+subtest "Validating a new jobset appears" => sub {
+    my $jobset = $project->jobsets->find({ name => "my-jobset" });
+    ok($jobset, "We have a jobset");
+    is($jobset->description, "my-declarative-jobset", "The jobset's description matches");
+
+    subtest "Evaluating and building that jobset works" => sub {
+        ok(evalSucceeds($jobset), "Evaluating the new jobset with return code 0");
+        is(nrQueuedBuildsForJobset($jobset), 1, "We should have exactly 1 build queued");
+
+        (my $build) = queuedBuildsForJobset($jobset);
+
+        is($build->job, "one_job", "The only job should be jobsets");
+        ok(runBuild($build), "Build should exit with return code 0");
+        my $newbuild = $db->resultset('Builds')->find($build->id);
+        is($newbuild->finished, 1, "Build should be finished.");
+        is($newbuild->buildstatus, 0, "Build should have buildstatus 0.");
+    };
+};
+done_testing;
diff --git a/t/jobs/declarative/generator.nix b/t/jobs/declarative/generator.nix
new file mode 100644
index 00000000..278dd9b6
--- /dev/null
+++ b/t/jobs/declarative/generator.nix
@@ -0,0 +1,29 @@
+{ jobspath, ... }:
+with import ../config.nix;
+{
+  jobsets = mkDerivation {
+    name = "jobsets";
+    builder = ./generator.sh;
+    jobsets = builtins.toJSON {
+      my-jobset = {
+        enabled = 1;
+        hidden = false;
+        description = "my-declarative-jobset";
+        nixexprinput = "src";
+        nixexprpath = "one-job.nix";
+        checkinterval = 300;
+        schedulingshares = 100;
+        enableemail = false;
+        emailoverride = "";
+        keepnr = 3;
+        inputs = {
+          src = {
+            type = "path";
+            value = jobspath;
+            emailresponsible = false;
+          };
+        };
+      };
+    };
+  };
+}
diff --git a/t/jobs/declarative/generator.sh b/t/jobs/declarative/generator.sh
new file mode 100755
index 00000000..51c0f0f5
--- /dev/null
+++ b/t/jobs/declarative/generator.sh
@@ -0,0 +1,3 @@
+#! /bin/sh
+
+echo "$jobsets" > $out