Add test for BUILD_COMMAND environment variable override

Author: Malax

test/spec/config_spec.rb

@@ -27,4 +27,18 @@
       end
     end
   end
+
+  it 'respects BUILD_COMMAND environment variable override' do
+    new_default_hatchet_runner('lein-2.x-with-uberjar').tap do |app|
+      app.before_deploy do
+        app.set_config('BUILD_COMMAND' => 'echo "Custom build command executed" && lein deps')
+      end
+
+      app.deploy do
+        expect(clean_output(app.output)).to include('Running: echo "Custom build command executed" && lein deps')
+        expect(clean_output(app.output)).to include('Custom build command executed')
+        expect(clean_output(app.output)).not_to include('Running: lein uberjar')
+      end
+    end
+  end
 end