diff --git a/tests/tests/connectors/test-class-connector-installer.php b/tests/tests/connectors/test-class-connector-installer.php
new file mode 100644
index 00000000..76157842
--- /dev/null
+++ b/tests/tests/connectors/test-class-connector-installer.php
@@ -0,0 +1,248 @@
+<?php
+/**
+ * Tests for Installer Connector class callbacks.
+ */
+namespace WP_Stream;
+
+class Test_WP_Stream_Connector_Installer extends WP_StreamTestCase {
+
+	/**
+	 * Runs before each test
+	 */
+	public function setUp() {
+		parent::setUp();
+
+		// Make partial of Connector_Installer class, with mocked "log" function.
+		$this->mock = $this->getMockBuilder( Connector_Installer::class )
+			->setMethods( array( 'log' ) )
+			->getMock();
+
+		// Register connector.
+		$this->mock->register();
+	}
+
+	public function test_callback_upgrader_process_complete() {
+		// Prepare scenario
+		$this->markTestSkipped( 'This test skipped until the needed scenario can be properly simulated.' );
+
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->withConsecutive(
+				array(
+					_x(
+						'Installed %1$s: %2$s %3$s',
+						'Plugin/theme installation. 1: Type (plugin/theme), 2: Plugin/theme name, 3: Plugin/theme version',
+						'stream'
+					),
+					array(
+						'type'        => 'plugin',
+						'name'        => 'Hello Dolly',
+						'version'     => '',
+						'slug'        => 'hello_dolly.php',
+						'success'     => true,
+						'error'       => null,
+						'old_version' => '',
+					),
+					null,
+					'plugins',
+					'installed'
+				),
+				array(
+					_x(
+						'Updated %1$s: %2$s %3$s',
+						'Plugin/theme update. 1: Type (plugin/theme), 2: Plugin/theme name, 3: Plugin/theme version',
+						'stream'
+					),
+					array(
+						'type'        => 'theme',
+						'name'        => 'Twenty Twenty',
+						'version'     => '',
+						'slug'        => 'twentytwenty',
+						'success'     => true,
+						'error'       => null,
+						'old_version' => '',
+					),
+					null,
+					'themes',
+					'updated'
+				)
+			);
+
+		// Simulate installing plugin and updating theme to trigger callback.
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_upgrader_process_complete' ) );
+	}
+
+	public function test_callback_activate_plugin() {
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'"%1$s" plugin activated %2$s',
+						'1: Plugin name, 2: Single site or network wide',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					array(
+						'name'         => 'Hello Dolly',
+						'network_wide' => null
+					)
+				),
+				$this->equalTo( null ),
+				$this->equalTo( 'plugins' ),
+				$this->equalTo( 'activated' )
+			);
+
+		// Do stuff.
+		\activate_plugin( 'hello.php' );
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_activate_plugin' ) );
+	}
+
+	public function test_callback_deactivate_plugin() {
+		// Prepare scenario
+		\activate_plugin( 'hello.php' );
+
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'"%1$s" plugin deactivated %2$s',
+						'1: Plugin name, 2: Single site or network wide',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					array(
+						'name'         => 'Hello Dolly',
+						'network_wide' => null,
+					)
+				),
+				$this->equalTo( null ),
+				$this->equalTo( 'plugins' ),
+				$this->equalTo( 'deactivated' )
+			);
+
+		// Do stuff.
+		\deactivate_plugins( array( 'hello.php' ) );
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_deactivate_plugin' ) );
+	}
+
+	public function test_callback_switch_theme() {
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->with(
+				$this->equalTo( __( '"%s" theme activated', 'stream' ) ),
+				$this->equalTo( array( 'name' => 'Twenty Twenty' ) ),
+				$this->equalTo( null ),
+				$this->equalTo( 'themes' ),
+				$this->equalTo( 'activated' )
+			);
+
+		// Do stuff.
+		switch_theme( 'twentytwenty' );
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_switch_theme' ) );
+	}
+
+	public function test_callback_delete_site_transient_update_themes() {
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->with(
+				$this->equalTo( __( '"%s" theme deleted', 'stream' ) ),
+				$this->equalTo( array( 'name' => 'twentyninteen' ) ),
+				$this->equalTo( null ),
+				$this->equalTo( 'themes' ),
+				$this->equalTo( 'deleted' )
+			);
+
+		// Do stuff.
+		delete_theme( 'twentyninteen' );
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_delete_site_transient_update_themes' ) );
+	}
+
+	public function test_callback_pre_set_site_transient_update_plugins() {
+		// Prepare scenario
+		$this->markTestSkipped( 'This test skipped until the needed scenario can be properly simulated.' );
+
+		// Expected log calls.
+		$this->mock->expects( $this->once() )
+			->method( 'log' )
+			->with(
+				$this->equalTo( __( '"%s" plugin deleted', 'stream' ) ),
+				$this->equalTo(
+					array(
+						'name'         => 'Hello Dolly',
+						'plugin'       => 'hello.php',
+						'network_wide' => null,
+					)
+				),
+				$this->equalTo( null ),
+				$this->equalTo( 'plugins' ),
+				$this->equalTo( 'deleted' )
+			);
+
+		// Do stuff.
+
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_pre_set_site_transient_update_plugins' ) );
+	}
+
+	public function test_callback__core_updated_successfully() {
+		// Prepare scenario
+		$this->markTestSkipped( 'This test skipped until the needed scenario can be properly simulated.' );
+
+		// Expected log calls.
+		$this->mock->expects( $this->exactly( 2 ) )
+			->method( 'log' )
+			->withConsecutive(
+				array(
+					$this->equalTo( esc_html__( 'WordPress auto-updated to %s', 'stream' ) ),
+					$this->equalTo(
+						array(
+							'new_version'  => '',
+							'old_version'  => '',
+							'auto_updated' => true,
+						)
+					),
+					$this->equalTo( null ),
+					$this->equalTo( 'WordPress' ),
+					$this->equalTo( 'updated' )
+				),
+				array(
+					$this->equalTo( esc_html__( 'WordPress updated to %s', 'stream' ) ),
+					$this->equalTo(
+						array(
+							'new_version'  => '',
+							'old_version'  => '',
+							'auto_updated' => false,
+						)
+					),
+					$this->equalTo( null ),
+					$this->equalTo( 'WordPress' ),
+					$this->equalTo( 'updated' )
+				)
+			);
+
+		// Do stuff.
+
+		// Check callback test action.
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback__core_updated_successfully' ) );
+	}
+}