Formula plugin coverage. (#353)

formula/src/test/java/com/instacart/formula/FormulaPluginTest.kt

@@ -0,0 +1,78 @@
+package com.instacart.formula
+
+import com.google.common.truth.Truth.assertThat
+import com.instacart.formula.internal.ClearPluginsRule
+import com.instacart.formula.plugin.Dispatcher
+import com.instacart.formula.plugin.Plugin
+import com.instacart.formula.subjects.IncrementingDispatcher
+import org.junit.Rule
+import org.junit.Test
+
+class FormulaPluginTest {
+
+    private class TestPlugin(
+        private val mainDispatcher: Dispatcher? = null,
+        private val backgroundDispatcher: Dispatcher? = null,
+        private val defaultDispatcher: Dispatcher? = null,
+    ) : Plugin {
+        override fun mainThreadDispatcher(): Dispatcher? {
+            return mainDispatcher ?: super.mainThreadDispatcher()
+        }
+
+        override fun backgroundThreadDispatcher(): Dispatcher? {
+            return backgroundDispatcher ?: super.backgroundThreadDispatcher()
+        }
+
+        override fun defaultDispatcher(): Dispatcher? {
+            return defaultDispatcher ?: super.defaultDispatcher()
+        }
+    }
+
+    @get:Rule
+    val rule = ClearPluginsRule()
+
+    @Test fun `when no plugin is specified, default dispatcher is none`() {
+        assertThat(FormulaPlugins.defaultDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `when plugin returns null, default dispatcher is none`() {
+        FormulaPlugins.setPlugin(TestPlugin())
+        assertThat(FormulaPlugins.defaultDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `plugin can override default dispatcher`() {
+        val myDispatcher = IncrementingDispatcher()
+        FormulaPlugins.setPlugin(TestPlugin(defaultDispatcher = myDispatcher))
+        assertThat(FormulaPlugins.defaultDispatcher()).isEqualTo(myDispatcher)
+    }
+
+    @Test fun `when no plugin is specified, default background dispatcher is none`() {
+        assertThat(FormulaPlugins.backgroundThreadDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `when plugin returns null, default background dispatcher is none`() {
+        FormulaPlugins.setPlugin(TestPlugin())
+        assertThat(FormulaPlugins.backgroundThreadDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `plugin can override background dispatcher`() {
+        val myDispatcher = IncrementingDispatcher()
+        FormulaPlugins.setPlugin(TestPlugin(backgroundDispatcher = myDispatcher))
+        assertThat(FormulaPlugins.backgroundThreadDispatcher()).isEqualTo(myDispatcher)
+    }
+
+    @Test fun `when plugin is null, default main dispatcher is none`() {
+        assertThat(FormulaPlugins.mainThreadDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `when plugin returns null, default main dispatcher is none`() {
+        FormulaPlugins.setPlugin(TestPlugin())
+        assertThat(FormulaPlugins.mainThreadDispatcher()).isEqualTo(Dispatcher.None)
+    }
+
+    @Test fun `plugin can override main dispatcher`() {
+        val myDispatcher = IncrementingDispatcher()
+        FormulaPlugins.setPlugin(TestPlugin(mainDispatcher = myDispatcher))
+        assertThat(FormulaPlugins.mainThreadDispatcher()).isEqualTo(myDispatcher)
+    }
+}