diff --git a/src/unit/engine/PytestTestEngine.php b/src/unit/engine/PytestTestEngine.php
--- a/src/unit/engine/PytestTestEngine.php
+++ b/src/unit/engine/PytestTestEngine.php
@@ -13,7 +13,16 @@
     $cover_tmp = new TempFile();
 
     $future = $this->buildTestFuture($junit_tmp, $cover_tmp);
-    $future->resolvex();
+    list($err, $stdout, $stderr) = $future->resolve();
+
+    if (!Filesystem::pathExists($junit_tmp)) {
+      throw new CommandException(
+        "Command failed with error #{$err}!",
+        $future->getCommand(),
+        $err,
+        $stdout,
+        $stderr);
+    }
 
     $future = new ExecFuture('coverage xml -o %s', $cover_tmp);
     $future->setCWD($this->project_root);