diff --git a/infection.json.dist b/infection.json.dist
new file mode 100644
index 0000000..a88fae0
--- /dev/null
+++ b/infection.json.dist
@@ -0,0 +1,11 @@
+{
+    "timeout": 10,
+    "source": {
+        "directories": [
+            "src"
+        ]
+    },
+    "logs": {
+        "text": "build/logs/infection-log.txt"
+    }
+}
diff --git a/tests/Adapting_a_network.php b/tests/Adapting_a_network.php
index 9786326..cea2371 100644
--- a/tests/Adapting_a_network.php
+++ b/tests/Adapting_a_network.php
@@ -45,6 +45,37 @@ function finding_paths_through_a_simple_undirected_graph()
         $this->assertSame(['A', 'C', 'D'], $shortestPathFromA['D']);
     }
 
+    /** @test */
+    function finding_paths_through_a_simple_undirected_graph_with_numeric_ids()
+    {
+        $graph = new Graph();
+        $a = $graph->createVertex(1);
+        $b = $graph->createVertex(2);
+        $c = $graph->createVertex(3);
+        $d = $graph->createVertex(4);
+
+        $a->createEdgeTo($b)->setWeight(5);
+        $a->createEdgeTo($c)->setWeight(8);
+        $b->createEdgeTo($d)->setWeight(9);
+        $b->createEdgeTo($a)->setWeight(1);
+        $c->createEdgeTo($d)->setWeight(4);
+        $c->createEdgeTo($a)->setWeight(1);
+        $d->createEdgeTo($b)->setWeight(3);
+        $d->createEdgeTo($c)->setWeight(9);
+
+        $shortestPath = DynamicPathfinder::operatingIn(AdaptedNetwork::from($graph));
+
+        $this->assertEquals([1, 3, 4], $shortestPath->between('1', '4'));
+        $this->assertEquals([4, 2, 1], $shortestPath->between('4', '1'));
+
+        $shortestPathFromA = $shortestPath->from('1');
+
+        $this->assertCount(3, $shortestPathFromA);
+        $this->assertEquals([1, 2], $shortestPathFromA[2]);
+        $this->assertEquals([1, 3], $shortestPathFromA[3]);
+        $this->assertEquals([1, 3, 4], $shortestPathFromA[4]);
+    }
+
     /** @test */
     function finding_paths_through_a_simple_directed_graph()
     {
diff --git a/tests/Adapting_an_environment.php b/tests/Adapting_an_environment.php
index 72150c3..afb47bb 100644
--- a/tests/Adapting_an_environment.php
+++ b/tests/Adapting_an_environment.php
@@ -167,6 +167,44 @@ function finding_paths_through_a_directed_2d_multi_graph()
         $this->assertSame(['A', 'C', 'D'], $shortestPathFromA['D']);
     }
 
+    /** @test */
+    function finding_paths_through_a_directed_2d_multi_graph_with_numeric_ids()
+    {
+        $graph = new Graph();
+        $a = $graph->createVertex(1);
+        $a->setAttribute('x', 0);
+        $a->setAttribute('y', 0);
+        $b = $graph->createVertex(2);
+        $b->setAttribute('x', 4);
+        $b->setAttribute('y', 1);
+        $c = $graph->createVertex(3);
+        $c->setAttribute('x', 0);
+        $c->setAttribute('y', 8);
+        $d = $graph->createVertex(4);
+        $d->setAttribute('x', 5);
+        $d->setAttribute('y', 10);
+
+        $a->createEdge($b)->setWeight(5);
+        $a->createEdge($c)->setWeight(8);
+        $a->createEdge($c)->setWeight(15);
+        $b->createEdge($d)->setWeight(9);
+        $c->createEdge($d)->setWeight(4);
+
+        $shortestPath = DynamicPathfinder::operatingIn(
+            AdaptedEnvironment::from($graph)
+        );
+
+        $this->assertEquals([1, 3, 4], $shortestPath->between('1', '4'));
+        $this->assertEquals([4, 3, 1], $shortestPath->between('4', '1'));
+
+        $shortestPathFromA = $shortestPath->from('1');
+
+        $this->assertCount(3, $shortestPathFromA);
+        $this->assertEquals([1, 2], $shortestPathFromA[2]);
+        $this->assertEquals([1, 3], $shortestPathFromA[3]);
+        $this->assertEquals([1, 3, 4], $shortestPathFromA[4]);
+    }
+
     /** @test */
     function building_an_index_of_the_graph()
     {
diff --git a/tests/Unit/AdaptedEnvironmentTest.php b/tests/Unit/AdaptedEnvironmentTest.php
index 70a76d6..54858fe 100644
--- a/tests/Unit/AdaptedEnvironmentTest.php
+++ b/tests/Unit/AdaptedEnvironmentTest.php
@@ -89,4 +89,22 @@ function cannot_get_the_position_of_a_non_existing_node()
 
         $environment->positionOf('X');
     }
+
+    /** @test */
+    function all_undeclared_dimensions_are_seen_as_zero()
+    {
+        $graph = new Graph();
+        $a = $graph->createVertex('A');
+        $a->setAttribute('x', 10);
+        $a->setAttribute('y', 15);
+        $environment = AdaptedEnvironment::from3D($graph);
+
+        $position = $environment->positionOf('A');
+
+        $this->assertEquals(10, $position[0]);
+        $this->assertEquals(15, $position[1]);
+        $this->assertEquals(0, $position[2]);
+        $this->assertEquals(0, $position[3]);
+        $this->assertEquals(0, $position[391]);
+    }
 }
diff --git a/tests/Unit/AdaptedNetworkTest.php b/tests/Unit/AdaptedNetworkTest.php
index 6d0dce1..87bee11 100644
--- a/tests/Unit/AdaptedNetworkTest.php
+++ b/tests/Unit/AdaptedNetworkTest.php
@@ -73,7 +73,7 @@ function graphs_without_negatively_weighing_edges_have_no_negative_edge_costs()
         $graph = new Graph();
         $a = $graph->createVertex('A');
         $edge = $a->createEdge($a);
-        $edge->setWeight(1);
+        $edge->setWeight(0);
 
         $environment = AdaptedNetwork::from($graph);