diff --git a/includes/class-debug.php b/includes/class-debug.php
index eba51fd..81ab276 100644
--- a/includes/class-debug.php
+++ b/includes/class-debug.php
@@ -63,7 +63,7 @@ private static function verify_filesystem( $wp_filesystem ) {
 				/**
 				 * Log error in file write fails only if debug is set to true.  This is a valid use case.
 				 */
-				error_log( 'AspireUpdate - Could not open or write to the file system. Check file system permissions to debug log directory.' );
+				error_log( 'AspireUpdate - Could not open or write to the file system. Check file system permissions to debug log directory.' ); // @codeCoverageIgnore
 				// phpcs:enable
 			}
 			return false;
diff --git a/tests/phpunit/tests/Debug/Debug_ReadTest.php b/tests/phpunit/tests/Debug/Debug_ReadTest.php
new file mode 100644
index 0000000..5f275e1
--- /dev/null
+++ b/tests/phpunit/tests/Debug/Debug_ReadTest.php
@@ -0,0 +1,187 @@
+<?php
+/**
+ * Class Debug_ReadTest
+ *
+ * @package AspireUpdate
+ */
+
+/**
+ * Tests for Debug::read()
+ *
+ * @covers \AspireUpdate\Debug::read
+ */
+class Debug_ReadTest extends Debug_UnitTestCase {
+	/**
+	 * Test that a WP_Error object is returned when the filesystem isn't available.
+	 *
+	 * @covers \AspireUpdate\Debug::init_filesystem
+	 * @covers \AspireUpdate\Debug::verify_filesystem
+	 */
+	public function test_should_return_wp_error_when_filesystem_is_not_available() {
+		add_filter( 'filesystem_method', '__return_false' );
+		$this->assertWPError( AspireUpdate\Debug::read() );
+	}
+
+	/**
+	 * Test that a WP_Error object is returned when the log file doesn't exist.
+	 *
+	 * @covers \AspireUpdate\Debug::init_filesystem
+	 * @covers \AspireUpdate\Debug::verify_filesystem
+	 * @covers \AspireUpdate\Debug::get_file_path
+	 */
+	public function test_should_return_wp_error_when_log_file_does_not_exist() {
+		$this->assertWPError( AspireUpdate\Debug::read() );
+	}
+
+	/**
+	 * Test that a WP_Error object is returned when the log file isn't readable.
+	 *
+	 * @covers \AspireUpdate\Debug::init_filesystem
+	 * @covers \AspireUpdate\Debug::verify_filesystem
+	 * @covers \AspireUpdate\Debug::get_file_path
+	 */
+	public function test_should_return_wp_error_when_log_file_is_not_readable() {
+		global $wp_filesystem;
+
+		// Create the log file.
+		file_put_contents( self::$log_file, '' );
+
+		// Backup and replace the filesystem object.
+		$wp_filesystem = $this->get_fake_filesystem( true, false, true );
+
+		$actual = AspireUpdate\Debug::read();
+
+		$this->assertWPError( $actual );
+	}
+
+	/**
+	 * Test that an empty log message is returned when the log file is empty.
+	 */
+	public function test_should_return_an_empty_log_message_when_log_file_is_empty() {
+		file_put_contents( self::$log_file, '' );
+
+		$actual = AspireUpdate\Debug::read();
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringContainsString(
+			'Log file is empty',
+			$actual,
+			'The empty log file message was not returned.'
+		);
+	}
+
+	/**
+	 * Test that an empty log message is returned when the log file's content
+	 * is only empty space.
+	 */
+	public function test_should_return_an_empty_log_message_when_log_file_only_has_empty_space() {
+		file_put_contents( self::$log_file, " \n\r\t\v\x00" );
+
+		$actual = AspireUpdate\Debug::read();
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringContainsString(
+			'Log file is empty',
+			$actual,
+			'The empty log file message was not returned.'
+		);
+	}
+
+	/**
+	 * Test that an empty log message is not returned when the log file
+	 * has contents.
+	 */
+	public function test_should_not_return_an_empty_log_message_when_log_file_has_contents() {
+		file_put_contents( self::$log_file, 'Some contents' );
+
+		$actual = AspireUpdate\Debug::read();
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringNotContainsString(
+			'Log file is empty',
+			$actual,
+			'The empty log file message was returned.'
+		);
+	}
+
+	/**
+	 * Test that a truncation message is added when the log file has more
+	 * lines than requested.
+	 */
+	public function test_should_add_a_truncation_message_when_log_file_has_more_lines_than_requested() {
+		file_put_contents(
+			self::$log_file,
+			"First line\r\nSecond line\r\nThird line"
+		);
+
+		$actual = AspireUpdate\Debug::read( 2 );
+
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringContainsString(
+			'Log truncated',
+			$actual,
+			'The truncation message was not returned.'
+		);
+	}
+
+	/**
+	 * Test that no truncation message is added when the log file has the same
+	 * number of lines as requested.
+	 */
+	public function test_should_not_add_a_truncation_message_when_log_file_has_the_same_number_of_lines_as_requested() {
+		file_put_contents(
+			self::$log_file,
+			"First line\r\nSecond line\r\nThird line"
+		);
+
+		$actual = AspireUpdate\Debug::read( 3 );
+
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringNotContainsString(
+			'Log truncated',
+			$actual,
+			'The truncation message was added.'
+		);
+	}
+
+	/**
+	 * Test that no truncation message is added when the log file has fewer than
+	 * lines than requested.
+	 */
+	public function test_should_not_add_a_truncation_message_when_log_file_has_fewer_lines_than_requested() {
+		file_put_contents(
+			self::$log_file,
+			"First line\r\nSecond line\r\nThird line"
+		);
+
+		$actual = AspireUpdate\Debug::read( 4 );
+
+		$this->assertIsString(
+			$actual,
+			'A string was not returned.'
+		);
+
+		$this->assertStringNotContainsString(
+			'Log truncated',
+			$actual,
+			'The truncation message was added.'
+		);
+	}
+}