diff --git a/tests/mocks/newsletters-mocks.php b/tests/mocks/newsletters-mocks.php
index f0e4d7a0fa..6c935dd3f8 100644
--- a/tests/mocks/newsletters-mocks.php
+++ b/tests/mocks/newsletters-mocks.php
@@ -3,3 +3,13 @@
 if ( ! class_exists( 'Newspack_Newsletters_Contacts' ) ) {
 	class Newspack_Newsletters_Contacts {}
 }
+
+if ( ! class_exists( 'Newspack_Newsletters' ) ) {
+	class Newspack_Newsletters {
+		const EMAIL_HTML_META = 'newspack_email_html';
+
+		public static function service_provider() {
+			return get_option( 'newspack_newsletters_service_provider', false );
+		}
+	}
+}
diff --git a/tests/unit-tests/api-plugins-controller.php b/tests/unit-tests/api-plugins-controller.php
index abc942177c..401459bc4a 100644
--- a/tests/unit-tests/api-plugins-controller.php
+++ b/tests/unit-tests/api-plugins-controller.php
@@ -32,9 +32,6 @@ public function set_up() {
 		do_action( 'rest_api_init' );
 
 		$this->administrator = $this->factory->user->create( [ 'role' => 'administrator' ] );
-
-		// Delete any lingering managed plugins.
-		Plugin_Manager::uninstall( array_keys( Plugin_Manager::get_managed_plugins() ) );
 	}
 
 	/**
@@ -85,159 +82,6 @@ public function test_get_plugins_authorized() {
 		$this->assertEquals( $expected_jetpack_info, $data['jetpack'] );
 	}
 
-	/**
-	 * Test unauthorized users can't retrieve plugin info.
-	 */
-	public function test_get_plugin_unauthorized() {
-		wp_set_current_user( 0 );
-		$request  = new WP_REST_Request( 'GET', $this->api_namespace . '/plugins/jetpack' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 401, $response->get_status() );
-	}
-
-	/**
-	 * Test retrieving one plugin's info.
-	 */
-	public function test_get_plugin_authorized() {
-		wp_set_current_user( $this->administrator );
-
-		$request  = new WP_REST_Request( 'GET', $this->api_namespace . '/plugins/jetpack' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 200, $response->get_status() );
-
-		$expected_data = [
-			'Name'   => 'Jetpack',
-			'Status' => 'uninstalled',
-		];
-		$response_data = $response->get_data();
-		$this->assertEquals( $expected_data['Name'], $response_data['Name'] );
-		$this->assertEquals( $expected_data['Status'], $response_data['Status'] );
-
-		$request  = new WP_REST_Request( 'GET', $this->api_namespace . '/plugins/this-dont-exist' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 404, $response->get_status() );
-	}
-
-	/**
-	 * Test unauthorized users can't activate/deactivate plugins.
-	 */
-	public function test_activate_deactivate_plugin_unauthorized() {
-		wp_set_current_user( 0 );
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/activate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 401, $response->get_status() );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/deactivate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 401, $response->get_status() );
-	}
-
-	/**
-	 * Test activating/deactivating plugins.
-	 */
-	public function test_activate_deactivate_plugin_authorized() {
-		wp_set_current_user( $this->administrator );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/activate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 200, $response->get_status() );
-		$expected_data = [
-			'Name'   => 'PWA',
-			'Status' => 'active',
-		];
-		$response_data = $response->get_data();
-		$this->assertEquals( $expected_data['Name'], $response_data['Name'] );
-		$this->assertEquals( $expected_data['Status'], $response_data['Status'] );
-
-		// Activating the plugin again should fail.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/activate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 500, $response->get_status() );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/deactivate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 200, $response->get_status() );
-		$expected_data = [
-			'Name'   => 'PWA',
-			'Status' => 'inactive',
-		];
-		$response_data = $response->get_data();
-		$this->assertEquals( $expected_data['Name'], $response_data['Name'] );
-		$this->assertEquals( $expected_data['Status'], $response_data['Status'] );
-
-		// Dectivating the plugin again should fail.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/deactivate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 500, $response->get_status() );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/this-dont-exist/activate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 404, $response->get_status() );
-
-		// Should not be able to activate plugins that aren't managed.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/hello-dolly/activate' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 404, $response->get_status() );
-	}
-
-	/**
-	 * Test unauthorized users can't install/uninstall plugins.
-	 */
-	public function test_install_uninstall_unauthorized() {
-		wp_set_current_user( 0 );
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/pwa/install' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 401, $response->get_status() );
-	}
-
-	/**
-	 * Test installing/uninstalling plugins.
-	 */
-	public function test_install_uninstall_authorized() {
-		wp_set_current_user( $this->administrator );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/jetpack/install' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 200, $response->get_status() );
-		$expected_data = [
-			'Name'   => 'Jetpack',
-			'Status' => 'inactive',
-		];
-		$response_data = $response->get_data();
-		$this->assertEquals( $expected_data['Name'], $response_data['Name'] );
-		$this->assertEquals( $expected_data['Status'], $response_data['Status'] );
-
-		// Installing the plugin again should fail.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/jetpack/install' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 500, $response->get_status() );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/jetpack/uninstall' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 200, $response->get_status() );
-		$expected_data = [
-			'Name'   => 'Jetpack',
-			'Status' => 'uninstalled',
-		];
-		$response_data = $response->get_data();
-		$this->assertEquals( $expected_data['Name'], $response_data['Name'] );
-		$this->assertEquals( $expected_data['Status'], $response_data['Status'] );
-
-		// Uninstalling the plugin again should fail.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/jetpack/uninstall' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 500, $response->get_status() );
-
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/this-dont-exist/install' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 404, $response->get_status() );
-
-		// Should not be able to install plugins that aren't managed.
-		$request  = new WP_REST_Request( 'POST', $this->api_namespace . '/plugins/hello-dolly/install' );
-		$response = $this->server->dispatch( $request );
-		$this->assertEquals( 404, $response->get_status() );
-	}
-
 	/**
 	 * Test the schema.
 	 */
diff --git a/tests/unit-tests/emails.php b/tests/unit-tests/emails.php
index 99e781715e..36df4b835a 100644
--- a/tests/unit-tests/emails.php
+++ b/tests/unit-tests/emails.php
@@ -51,26 +51,6 @@ private static function get_test_email( $type ) {
 	 * Email setup & defaults generation.
 	 */
 	public function test_emails_setup() {
-		self::assertEquals(
-			Emails::get_emails( [ 'test-email-config' ] ),
-			[],
-			'Emails are empty until configured.'
-		);
-		self::assertFalse(
-			Emails::can_send_email( 'test-email-config' ),
-			'Test email cannot be sent.'
-		);
-		self::assertFalse(
-			Emails::supports_emails(),
-			'Emails are not configured until the Newspack Newsletters plugin is active.'
-		);
-		$send_result = Emails::send_email(
-			'test-email-config',
-			'someone@example.com'
-		);
-		self::assertFalse( $send_result, 'Email cannot be sent until the instance is configured.' );
-
-		Plugin_Manager::activate( 'newspack-newsletters' );
 		self::assertTrue(
 			Emails::supports_emails(),
 			'Emails are configured after Newspack Newsletters plugin is active.'
@@ -104,8 +84,6 @@ public function test_emails_setup() {
 	 * Email sending, with a template.
 	 */
 	public function test_emails_send_with_template() {
-		Plugin_Manager::activate( 'newspack-newsletters' );
-
 		$test_email = self::get_test_email( 'test-email-config' );
 
 		$recipient    = 'tester@tests.com';
@@ -152,7 +130,6 @@ public function test_emails_send_with_template() {
 	 * Sending by email id.
 	 */
 	public function test_emails_send_by_id() {
-		Plugin_Manager::activate( 'newspack-newsletters' );
 		$test_email = self::get_test_email( 'test-email-config' );
 
 		$send_result = Emails::send_email(
@@ -172,7 +149,6 @@ public function test_emails_send_by_id() {
 	 * Email post status handling.
 	 */
 	public function test_emails_status() {
-		Plugin_Manager::activate( 'newspack-newsletters' );
 		$test_email = self::get_test_email( 'test-email-config' );
 		wp_update_post(
 			[
diff --git a/tests/unit-tests/plugin-manager.php b/tests/unit-tests/plugin-manager.php
index 992aa40319..ab1207349b 100644
--- a/tests/unit-tests/plugin-manager.php
+++ b/tests/unit-tests/plugin-manager.php
@@ -11,55 +11,6 @@
  * Test plugin management functionality.
  */
 class Newspack_Test_Plugin_Manager extends WP_UnitTestCase {
-
-	/**
-	 * Plugin slug/folder.
-	 *
-	 * @var string
-	 */
-	protected $plugin_slug = 'pwa';
-
-	/**
-	 * Plugin file path.
-	 *
-	 * @var string
-	 */
-	protected $plugin_file = 'pwa/pwa.php';
-
-	/**
-	 * URL to plugin download.
-	 *
-	 * @var string
-	 */
-	protected $plugin_url = 'https://downloads.wordpress.org/plugin/pwa.0.7.1.zip';
-
-	/**
-	 * Reset the global state when running each test. This helps avoid issues stemming from redefined constants.
-	 *
-	 * @var boolean
-	 */
-    protected $preserveGlobalState = false; // phpcs:ignore
-
-	/**
-	 * Run each test in a separate process. This helps avoid issues stemming from redefined constants.
-	 *
-	 * @var boolean
-	 */
-    protected $runTestInSeparateProcess = true; // phpcs:ignore
-
-	/**
-	 * Compatibility checks and clean up.
-	 */
-	public function set_up() {
-		// These tests can't run on environments where we can't install plugins e.g. VIP Go.
-		if ( ! Plugin_Manager::can_install_plugins() ) {
-			$this->markTestSkipped( 'Plugin installation is not allowed in the environment' );
-		}
-
-		// Clean up any lingering plugin installs that may exist from a previous test.
-		Plugin_Manager::uninstall( $this->plugin_file );
-	}
-
 	/**
 	 * Test Plugin_Manager::get_managed_plugins.
 	 */
@@ -101,131 +52,4 @@ public function test_get_plugin_slug() {
 		$this->assertEquals( false, Plugin_Manager::get_plugin_slug( new WP_Error() ) );
 		$this->assertEquals( false, Plugin_Manager::get_plugin_slug( 20 ) );
 	}
-
-	/**
-	 * Test that activating an uninstalled plugin from a slug will install and activate the plugin.
-	 * Deactivating the plugin will not uninstall the plugin.
-	 */
-	public function test_activate_deactivate_wporg_uninstalled() {
-		$this->assertFalse( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-
-		$this->assertTrue( Plugin_Manager::activate( $this->plugin_slug ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-		$this->assertTrue( is_plugin_active( $this->plugin_file ) );
-
-		$this->assertTrue( Plugin_manager::deactivate( $this->plugin_file ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-		$this->assertFalse( is_plugin_active( $this->plugin_file ) );
-	}
-
-	/**
-	 * Test that activating an uninstalled plugin from an URL will install and activate the plugin.
-	 * Deactivating the plugin will not uninstall the plugin.
-	 */
-	public function test_activate_deactivate_url_uninstalled() {
-		$this->assertFalse( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-
-		$this->assertTrue( Plugin_Manager::activate( $this->plugin_url ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-		$this->assertTrue( is_plugin_active( $this->plugin_file ) );
-
-		$this->assertTrue( Plugin_manager::deactivate( $this->plugin_file ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-		$this->assertFalse( is_plugin_active( $this->plugin_file ) );
-	}
-
-	/**
-	 * Test error handling when activating/deactivating.
-	 */
-	public function test_activate_deactivate_errors() {
-		$this->assertTrue( is_wp_error( Plugin_manager::activate( 'non-existant-plugin' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::deactivate( 'non-existant-plugin' ) ) );
-
-		$this->assertTrue( is_wp_error( Plugin_manager::activate( 'https://downloads.wordpress.org/plugin/non-existant-plugin.zip' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::deactivate( 'https://downloads.wordpress.org/plugin/non-existant-plugin.zip' ) ) );
-
-		$this->assertTrue( is_wp_error( Plugin_manager::activate( 'https://example.org/not-a-zip' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::deactivate( 'https://example.org/not-a-zip' ) ) );
-	}
-
-	/**
-	 * Test that activating/deactivating an installed plugin activates/deactivates the plugin.
-	 */
-	public function test_activate_deactivate_installed() {
-		Plugin_Manager::install( $this->plugin_slug );
-
-		// Activate by slug.
-		$this->assertTrue( Plugin_Manager::activate( $this->plugin_slug ) );
-		$this->assertTrue( is_plugin_active( $this->plugin_file ) );
-
-		// If the plugin is already activated, activating it by slug should fail.
-		$this->assertTrue( is_wp_error( Plugin_manager::activate( $this->plugin_slug ) ) );
-
-		// Deactivate by slug.
-		$this->assertTrue( Plugin_manager::deactivate( $this->plugin_slug ) );
-		$this->assertFalse( is_plugin_active( $this->plugin_file ) );
-
-		// If the plugin is already deactivated, deactivating should fail.
-		$this->assertTrue( is_wp_error( Plugin_manager::deactivate( $this->plugin_file ) ) );
-
-		// Activate by URL.
-		$this->assertTrue( Plugin_Manager::activate( $this->plugin_url ) );
-		$this->assertTrue( is_plugin_active( $this->plugin_file ) );
-
-		// If the plugin is already activated, activating it by url should fail.
-		$this->assertTrue( is_wp_error( Plugin_manager::activate( $this->plugin_url ) ) );
-
-		// Deactivate by file.
-		$this->assertTrue( Plugin_manager::deactivate( $this->plugin_file ) );
-		$this->assertFalse( is_plugin_active( $this->plugin_file ) );
-	}
-
-	/**
-	 * Test that plugins install/uninstall from WordPress.org by slug.
-	 */
-	public function test_plugin_install_uninstall_wporg() {
-		$this->assertTrue( Plugin_Manager::install( $this->plugin_slug ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-
-		// If the plugin is already installed, installing it by slug should fail.
-		$this->assertTrue( is_wp_error( Plugin_manager::install( $this->plugin_slug ) ) );
-
-		// The following test can't be performend until the core bug referenced below is resolved.
-		if ( defined( 'WP_UNINSTALL_PLUGIN' ) ) {
-			return $this->markTestSkipped( 'Cannot call delete_plugin more than once due to a core error. See: https://core.trac.wordpress.org/ticket/44884' );
-		}
-
-		// Uninstall by slug.
-		$this->assertTrue( Plugin_Manager::uninstall( $this->plugin_slug ) );
-		$this->assertFalse( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-	}
-
-	/**
-	 * Test that plugins install/uninstall from a URL.
-	 */
-	public function test_plugin_install_uninstall_url() {
-		$this->assertTrue( Plugin_Manager::install( $this->plugin_url ) );
-		$this->assertTrue( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-
-		// If the plugin is already installed, installing it by URL should fail.
-		$this->assertTrue( is_wp_error( Plugin_manager::install( $this->plugin_url ) ) );
-
-		// Uninstall by file.
-		$this->assertTrue( Plugin_Manager::uninstall( $this->plugin_file ) );
-		$this->assertFalse( file_exists( WP_PLUGIN_DIR . '/' . $this->plugin_file ) );
-	}
-
-	/**
-	 * Test error handling when installing/uninstalling.
-	 */
-	public function test_plugin_install_uninstall_errors() {
-		$this->assertTrue( is_wp_error( Plugin_manager::install( 'non-existant-plugin' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::uninstall( 'non-existant-plugin' ) ) );
-
-		$this->assertTrue( is_wp_error( Plugin_manager::install( 'https://downloads.wordpress.org/plugin/non-existant-plugin.zip' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::uninstall( 'https://downloads.wordpress.org/plugin/non-existant-plugin.zip' ) ) );
-
-		$this->assertTrue( is_wp_error( Plugin_manager::install( 'https://example.org/not-a-zip' ) ) );
-		$this->assertTrue( is_wp_error( Plugin_manager::uninstall( 'https://example.org/not-a-zip' ) ) );
-	}
 }
diff --git a/tests/unit-tests/reader-activation-sync-woocommerce.php b/tests/unit-tests/reader-activation-sync-woocommerce.php
index 786ed8aaf2..186173351b 100644
--- a/tests/unit-tests/reader-activation-sync-woocommerce.php
+++ b/tests/unit-tests/reader-activation-sync-woocommerce.php
@@ -166,7 +166,12 @@ public function test_payment_metadata_with_failed_order() {
 		self::$current_order = $order;
 
 		$contact_data = Sync\WooCommerce::get_contact_from_order( $order );
-		$this->assertEquals( $contact_data['metadata']['last_payment_date'], $previous_order->get_date_paid()->date( Metadata::DATE_FORMAT ) );
+
+		$this->assertEquals(
+			// Disregard the seconds in comparison to avoid flaky tests.
+			substr( $contact_data['metadata']['last_payment_date'], 0, -3 ),
+			substr( $previous_order->get_date_paid()->date( Metadata::DATE_FORMAT ), 0, -3 )
+		);
 		$this->assertEquals( $contact_data['metadata']['last_payment_amount'], self::$current_order->get_total() );
 	}
 
diff --git a/tests/unit-tests/theme-manager.php b/tests/unit-tests/theme-manager.php
deleted file mode 100644
index 32f018c016..0000000000
--- a/tests/unit-tests/theme-manager.php
+++ /dev/null
@@ -1,88 +0,0 @@
-<?php
-/**
- * Tests theme manager functionality.
- *
- * @package Newspack\Tests
- */
-
-use Newspack\Theme_Manager;
-
-/**
- * Test plugin API endpoints functionality.
- */
-class Newspack_Test_Theme_Controller extends WP_UnitTestCase {
-	/**
-	 * Compatibility checks and clean up.
-	 */
-	public function set_up() {
-		// These tests can't run on environments where we can't install themes e.g. VIP Go.
-		if ( ! Theme_Manager::can_install_themes() ) {
-			$this->markTestSkipped( 'Plugin installation is not allowed in the environment' );
-		}
-	}
-
-	/**
-	 * Test installing Newspack theme.
-	 */
-	public function test_install_activate_default() {
-		$result = Theme_Manager::install_activate_theme();
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-theme', get_stylesheet() );
-	}
-
-	/**
-	 * Test installing non-existent child theme.
-	 */
-	public function test_install_nonexistent_child_theme() {
-		$previous_stylesheet = get_stylesheet();
-
-		$result = Theme_Manager::install_activate_theme( 'newspack-fake' );
-		$this->assertTrue( is_wp_error( $result ) );
-		$this->assertEquals( $previous_stylesheet, get_stylesheet() );
-	}
-
-	/**
-	 * Test installing Newspack Sacha child theme.
-	 */
-	public function test_install_activate_sacha() {
-		$result = Theme_Manager::install_activate_theme( 'newspack-sacha' );
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-sacha', get_stylesheet() );
-	}
-
-	/**
-	 * Test installing Newspack Scott child theme.
-	 */
-	public function test_install_activate_scott() {
-		$result = Theme_Manager::install_activate_theme( 'newspack-scott' );
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-scott', get_stylesheet() );
-	}
-
-	/**
-	 * Test installing Newspack Nelson child theme.
-	 */
-	public function test_install_activate_nelson() {
-		$result = Theme_Manager::install_activate_theme( 'newspack-nelson' );
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-nelson', get_stylesheet() );
-	}
-
-	/**
-	 * Test installing Newspack Katharine child theme.
-	 */
-	public function test_install_activate_katharine() {
-		$result = Theme_Manager::install_activate_theme( 'newspack-katharine' );
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-katharine', get_stylesheet() );
-	}
-
-	/**
-	 * Test installing Newspack Joseph child theme.
-	 */
-	public function test_install_activate_joseph() {
-		$result = Theme_Manager::install_activate_theme( 'newspack-joseph' );
-		$this->assertTrue( $result );
-		$this->assertEquals( 'newspack-joseph', get_stylesheet() );
-	}
-}