Implemented features/install-in-pie-project.feature as Behat test

Author: asgrim

.github/pie-behaviour-tests/Dockerfile

@@ -3,7 +3,11 @@
 #
 # docker buildx build --file .github/pie-behaviour-tests/Dockerfile -t pie-behat-test .
 # docker run --volume .:/github/workspace -ti pie-behat-test
-FROM ubuntu:24.04
+FROM alpine/git:v2.49.1 AS clone_ext_repo
+
+RUN cd / && git clone https://github.com/asgrim/example-pie-extension.git
+
+FROM ubuntu:24.04 AS default
 
 # Add the `unzip` package which PIE uses to extract .zip files
 RUN export DEBIAN_FRONTEND="noninteractive"; \
@@ -36,6 +40,8 @@ RUN touch /usr/local/lib/php.ini
 COPY --from=ghcr.io/php/pie:bin /pie /usr/bin/pie
 RUN pie install xdebug/xdebug
 
+COPY --from=clone_ext_repo /example-pie-extension /example-pie-extension
+
 WORKDIR /github/workspace
 
 ENV USING_PIE_BEHAT_DOCKERFILE=1

test/behaviour/CliContext.php

@@ -357,4 +357,21 @@ public function iShouldSeeAllTheExtensionsAreNowInstalled(): void
         $this->assertCommandSuccessful();
         Assert::contains($this->output, 'example_pie_extension');
     }
+
+    #[Given('I am in a PIE project')]
+    public function iAmInAPIEProject(): void
+    {
+        $examplePieProject = (string) realpath('/example-pie-extension');
+        assert($examplePieProject !== '');
+
+        $this->workingDirectory = $examplePieProject;
+    }
+
+    #[When('I run a command to install the extension')]
+    public function iRunACommandToInstallTheExtension(): void
+    {
+        $this->theExtension = 'example_pie_extension';
+        $this->thePackage   = 'asgrim/example-pie-extension';
+        $this->runPieCommand(['install']);
+    }
 }