Improve tests around constituents

- Test how shorter names are preferred when multiple jobs resolve to the
  same derivation.

- Test the exact aggregate map we get, by looking in the DB.

t/evaluator/evaluate-constituents-gc.t

@@ -5,13 +5,58 @@ use Test2::V0;
 
 my $ctx = test_context();
 
-my $builds = $ctx->makeAndEvaluateJobset(
-    expression => 'constituents.nix',
+my $expression = 'constituents.nix';
+my $jobsetCtx = $ctx->makeJobset(
+    expression => $expression,
+);
+my $builds = $ctx->evaluateJobset(
+    jobset => $jobsetCtx->{"jobset"},
+    expression => $expression,
+    build => 0,
 );
 
 my $constituentA = $builds->{"constituentA"};
 my $directAggregate = $builds->{"direct_aggregate"};
 my $indirectAggregate = $builds->{"indirect_aggregate"};
+my $mixedAggregate = $builds->{"mixed_aggregate"};
+
+# Ensure that we get exactly the aggregates we expect
+my %expected_constituents = (
+    'direct_aggregate' => {
+        'constituentA' => 1,
+    },
+    'indirect_aggregate' => {
+        'constituentA' => 1,
+    },
+    'mixed_aggregate' => {
+        # Note that `constituentA_alias` becomes `constituentA`, because
+        # the shorter name is preferred
+        'constituentA' => 1,
+        'constituentB' => 1,
+    },
+);
+
+my $rs = $ctx->db->resultset('AggregateConstituents')->search(
+    {},
+    {
+        join     => [ 'aggregate', 'constituent' ],  # Use correct relationship names
+        columns  => [],
+        '+select' => [ 'aggregate.job', 'constituent.job' ],
+        '+as'     => [ 'aggregate_job', 'constituent_job' ],
+    }
+);
+
+my %actual_constituents;
+while (my $row = $rs->next) {
+    my $aggregate_job   = $row->get_column('aggregate_job');
+    my $constituent_job = $row->get_column('constituent_job');
+    $actual_constituents{$aggregate_job} //= {};
+    $actual_constituents{$aggregate_job}{$constituent_job} = 1;
+}
+
+is(\%actual_constituents, \%expected_constituents, "Exact aggregate constituents as expected");
+
+# Check that deletion also doesn't work accordingly
 
 is(system('nix-store', '--delete', $constituentA->drvpath), 256, "Deleting a constituent derivation fails");
 is(system('nix-store', '--delete', $directAggregate->drvpath), 256, "Deleting the direct aggregate derivation fails");

t/jobs/constituents.nix

@@ -5,6 +5,8 @@ rec {
     builder = ./empty-dir-builder.sh;
   };
 
+  constituentA_alias = constituentA;
+
   constituentB = mkDerivation {
     name = "empty-dir-B";
     builder = ./empty-dir-builder.sh;
@@ -32,7 +34,7 @@ rec {
     name = "mixed_aggregate";
     _hydraAggregate = true;
     constituents = [
-      "constituentA"
+      "constituentA_alias"
       constituentB
     ];
     builder = ./empty-dir-builder.sh;

t/lib/HydraTestContext.pm

@@ -172,7 +172,6 @@ sub makeAndEvaluateJobset {
     }
 
     my $jobsdir = $opts{'jobsdir'} // $self->jobsdir;
-    my $should_build = $opts{'build'} // 0;
 
     my %args = (
         jobsdir => $jobsdir,
@@ -184,12 +183,28 @@ sub makeAndEvaluateJobset {
         $args{flake} = $flake;
     }
     my $jobsetCtx = $self->makeJobset(%args);
-    my $jobset = $jobsetCtx->{"jobset"};
+
+    return $self->evaluateJobset(
+        jobset => $jobsetCtx->{"jobset"},
+        expression => $expression,
+        flake => $flake,
+        build => $opts{"build"} // 0,
+    )
+}
+
+sub evaluateJobset {
+    my ($self, %opts) = @_;
+
+    my $jobset = $opts{'jobset'};
+
+    my $expression = $opts{'expression'} // $opts{'flake'};
 
     evalSucceeds($jobset) or die "Evaluating jobs/$expression should exit with return code 0.\n";
 
     my $builds = {};
 
+    my $should_build = $opts{'build'};
+
     for my $build ($jobset->builds) {
         if ($should_build) {
             runBuild($build) or die "Build '".$build->job."' from jobs/$expression should exit with return code 0.\n";