implement simplified PluginManager API

scm-webapp/src/test/java/sonia/scm/plugin/PluginCenterLoaderTest.java

@@ -0,0 +1,50 @@
+package sonia.scm.plugin;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Answers;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import sonia.scm.net.ahc.AdvancedHttpClient;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.Set;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+@ExtendWith(MockitoExtension.class)
+class PluginCenterLoaderTest {
+
+  private static final String PLUGIN_URL = "https://plugins.hitchhiker.com";
+
+  @Mock(answer = Answers.RETURNS_DEEP_STUBS)
+  private AdvancedHttpClient client;
+
+  @Mock
+  private PluginCenterDtoMapper mapper;
+
+  @InjectMocks
+  private PluginCenterLoader loader;
+
+  @Test
+  void shouldFetch() throws IOException {
+    Set<AvailablePlugin> plugins = Collections.emptySet();
+    PluginCenterDto dto = new PluginCenterDto();
+    when(client.get(PLUGIN_URL).request().contentFromJson(PluginCenterDto.class)).thenReturn(dto);
+    when(mapper.map(dto)).thenReturn(plugins);
+
+    Set<AvailablePlugin> fetched = loader.load(PLUGIN_URL);
+    assertThat(fetched).isSameAs(plugins);
+  }
+
+  @Test
+  void shouldReturnEmptySetIfPluginCenterNotBeReached() throws IOException {
+    when(client.get(PLUGIN_URL).request()).thenThrow(new IOException("failed to fetch"));
+
+    Set<AvailablePlugin> fetch = loader.load(PLUGIN_URL);
+    assertThat(fetch).isEmpty();
+  }
+}