diff --git a/Slack.php b/Slack.php
index b35d80b..a428055 100644
--- a/Slack.php
+++ b/Slack.php
@@ -58,7 +58,7 @@ public function registerEvents()
             'ScheduledReports.sendReport' => 'sendReport',
             'Template.reportParametersScheduledReports' => 'templateReportParametersScheduledReports',
             'Translate.getClientSideTranslationKeys' => 'getClientSideTranslationKeys',
-            'CustomAlerts.validateReportParameters'  => 'validateCustomAlertReportParameters',
+            'CustomAlerts.validateReportParameters' => 'validateCustomAlertReportParameters',
             'CustomAlerts.sendNewAlerts' => 'sendNewAlerts',
         ];
     }
@@ -76,6 +76,16 @@ public function getClientSideTranslationKeys(&$translationKeys)
         $translationKeys[] = 'Slack_SlackEnterYourSlackChannelIdHelpText';
     }
 
+    /**
+     *
+     * Validates the Schedule Report for Slack reportType
+     *
+     * @param $parameters
+     * @param $reportType
+     * @return void
+     * @throws \Piwik\Exception\DI\DependencyException
+     * @throws \Piwik\Exception\DI\NotFoundException
+     */
     public function validateReportParameters(&$parameters, $reportType)
     {
         if (!self::isSlackEvent($reportType)) {
@@ -106,8 +116,23 @@ public function validateReportParameters(&$parameters, $reportType)
         } elseif (empty($parameters[self::SLACK_CHANNEL_ID_PARAMETER])) {
             throw new \Exception(Piwik::translate('Slack_SlackChannelIdRequiredErrorMessage'));
         }
+        $slackChannels = explode(',', (string) $parameters[self::SLACK_CHANNEL_ID_PARAMETER]);
+        foreach ($slackChannels as $slackChannel) {
+            if (!ctype_alnum($slackChannel)) {
+                throw new \Exception(Piwik::translate('Slack_SlackChannelIdInvalidErrorMessage'));
+            }
+        }
     }
 
+    /**
+     *
+     * Get report metadata for Slack scheduled report
+     *
+     * @param $availableReportMetadata
+     * @param $reportType
+     * @param $idSite
+     * @return void
+     */
     public function getReportMetadata(&$availableReportMetadata, $reportType, $idSite)
     {
         if (!self::isSlackEvent($reportType)) {
@@ -121,11 +146,26 @@ public function getReportMetadata(&$availableReportMetadata, $reportType, $idSit
         );
     }
 
+    /**
+     *
+     * Adds Slack as a reportType in Schedule Reports
+     *
+     * @param $reportTypes
+     * @return void
+     */
     public function getReportTypes(&$reportTypes)
     {
         $reportTypes = array_merge($reportTypes, self::$managedReportTypes);
     }
 
+    /**
+     *
+     * Adds allowed reportTypes for Slack, e.g. PDF, CSV and TSV
+     *
+     * @param $reportFormats
+     * @param $reportType
+     * @return void
+     */
     public function getReportFormats(&$reportFormats, $reportType)
     {
         if (self::isSlackEvent($reportType)) {
@@ -133,6 +173,14 @@ public function getReportFormats(&$reportFormats, $reportType)
         }
     }
 
+    /**
+     *
+     * Adds report parameter for Slack, e.g. SlackChannelID
+     *
+     * @param $availableParameters
+     * @param $reportType
+     * @return void
+     */
     public function getReportParameters(&$availableParameters, $reportType)
     {
         if (self::isSlackEvent($reportType)) {
@@ -140,6 +188,16 @@ public function getReportParameters(&$availableParameters, $reportType)
         }
     }
 
+    /**
+     *
+     * Process the Schedule report for reportType Slack
+     *
+     * @param $processedReports
+     * @param $reportType
+     * @param $outputType
+     * @param $report
+     * @return void
+     */
     public function processReports(&$processedReports, $reportType, $outputType, $report)
     {
         if (!self::isSlackEvent($reportType)) {
@@ -153,6 +211,17 @@ public function processReports(&$processedReports, $reportType, $outputType, $re
         );
     }
 
+    /**
+     *
+     * Sets the rendered instance based on reportFormat for Slack
+     *
+     * @param $reportRenderer
+     * @param $reportType
+     * @param $outputType
+     * @param $report
+     * @return void
+     * @throws \Exception
+     */
     public function getRendererInstance(&$reportRenderer, $reportType, $outputType, $report)
     {
         if (!self::isSlackEvent($reportType)) {
@@ -164,6 +233,14 @@ public function getRendererInstance(&$reportRenderer, $reportType, $outputType,
         $reportRenderer = ReportRenderer::factory($reportFormat);
     }
 
+    /**
+     *
+     * To allow multiple reports in a single file
+     *
+     * @param $allowMultipleReports
+     * @param $reportType
+     * @return void
+     */
     public function allowMultipleReports(&$allowMultipleReports, $reportType)
     {
         if (self::isSlackEvent($reportType)) {
@@ -171,6 +248,15 @@ public function allowMultipleReports(&$allowMultipleReports, $reportType)
         }
     }
 
+    /**
+     *
+     * Displays the recipients in the list of Schedule Reports
+     *
+     * @param $recipients
+     * @param $reportType
+     * @param $report
+     * @return void
+     */
     public function getReportRecipients(&$recipients, $reportType, $report)
     {
         if (!self::isSlackEvent($reportType) || empty($report['parameters'][self::SLACK_CHANNEL_ID_PARAMETER])) {
@@ -181,6 +267,9 @@ public function getReportRecipients(&$recipients, $reportType, $report)
     }
 
     /**
+     *
+     * Code to send a Schedule Report via Slack
+     *
      * @param $reportType
      * @param $report
      * @param $contents
@@ -189,8 +278,11 @@ public function getReportRecipients(&$recipients, $reportType, $report)
      * @param $reportSubject
      * @param $reportTitle
      * @param $additionalFiles
-     * @param Period|null $period
+     * @param $period
      * @param $force
+     * @return void
+     * @throws \Piwik\Exception\DI\DependencyException
+     * @throws \Piwik\Exception\DI\NotFoundException
      */
     public function sendReport(
         $reportType,
@@ -232,6 +324,16 @@ public function sendReport(
         $scheduleReportSlack->send();
     }
 
+    /**
+     *
+     * Add the view template for Slack report parameters
+     *
+     * @param $out
+     * @param $context
+     * @return void
+     * @throws \Piwik\Exception\DI\DependencyException
+     * @throws \Piwik\Exception\DI\NotFoundException
+     */
     public function templateReportParametersScheduledReports(&$out, $context = '')
     {
         if (Piwik::isUserIsAnonymous()) {
@@ -277,17 +379,42 @@ public function uninstall()
         return;
     }
 
+    /**
+     *
+     * Validation check for CustomAlert report parameters
+     *
+     * @param $parameters
+     * @param $alertMedium
+     * @return void
+     * @throws \Exception
+     */
     public function validateCustomAlertReportParameters($parameters, $alertMedium)
     {
-        if ($alertMedium === self::SLACK_TYPE && empty($parameters[self::SLACK_CHANNEL_ID_PARAMETER])) {
-            throw new \Exception(Piwik::translate('Slack_SlackChannelIdRequiredErrorMessage'));
+        if ($alertMedium === self::SLACK_TYPE) {
+            $settings = StaticContainer::get(SystemSettings::class);
+            if (empty($settings->slackOauthToken->getValue())) {
+                throw new \Exception(Piwik::translate('Slack_OauthTokenRequiredErrorMessage'));
+            } elseif (empty($parameters[self::SLACK_CHANNEL_ID_PARAMETER])) {
+                throw new \Exception(Piwik::translate('Slack_SlackChannelIdRequiredErrorMessage'));
+            } elseif (!ctype_alnum($parameters[self::SLACK_CHANNEL_ID_PARAMETER])) {
+                throw new \Exception(Piwik::translate('Slack_SlackChannelIdInvalidErrorMessage'));
+            }
         }
     }
 
+    /**
+     *
+     * Code to send CustomAlerts via Slack
+     *
+     * @param $triggeredAlerts
+     * @return void
+     * @throws \Piwik\Exception\DI\DependencyException
+     * @throws \Piwik\Exception\DI\NotFoundException
+     */
     public function sendNewAlerts($triggeredAlerts): void
     {
         if (!empty($triggeredAlerts)) {
-            $enrichTriggerAlerts = new EnrichTriggeredAlerts();
+            $enrichTriggerAlerts = StaticContainer::get(EnrichTriggeredAlerts::class);
             $triggeredAlerts = $enrichTriggerAlerts->enrichTriggeredAlerts($triggeredAlerts);
             $settings = StaticContainer::get(SystemSettings::class);
             $token = $settings->slackOauthToken->getValue();
@@ -305,6 +432,13 @@ public function sendNewAlerts($triggeredAlerts): void
         }
     }
 
+    /**
+     *
+     * Group alerts by slackChannelID to reduce number of network calls for multiple alerts
+     *
+     * @param array $alerts
+     * @return array
+     */
     private function groupAlertsByChannelId(array $alerts): array
     {
         $groupedAlerts = [];
@@ -321,11 +455,27 @@ private function groupAlertsByChannelId(array $alerts): array
         return $groupedAlerts;
     }
 
+    /**
+     *
+     * Returns the alert message to send via Slack
+     *
+     * @param array $alert
+     * @param string $metric
+     * @param string $reportName
+     * @return string
+     */
     public function getAlertMessage(array $alert, string $metric, string $reportName): string
     {
         return Piwik::translate('Slack_SlackAlertContent', [$alert['name'], $alert['siteName'], $metric, $reportName, $this->transformAlertCondition($alert)]);
     }
 
+    /**
+     *
+     * Transform the alert condition to text
+     *
+     * @param array $alert
+     * @return string
+     */
     private function transformAlertCondition(array $alert): string
     {
         switch ($alert['metric_condition']) {
diff --git a/SlackApi.php b/SlackApi.php
index ce7d520..02e6c3c 100644
--- a/SlackApi.php
+++ b/SlackApi.php
@@ -65,6 +65,14 @@ public function uploadFile(string $subject, string $fileName, string $fileConten
         return false;
     }
 
+    /**
+     *
+     * Get the URL to upload the file
+     *
+     * @param string $fileName
+     * @param int $fileLength
+     * @return string
+     */
     public function getUploadURLExternal(string $fileName, int $fileLength): string
     {
         try {
@@ -93,6 +101,14 @@ public function getUploadURLExternal(string $fileName, int $fileLength): string
         return '';
     }
 
+    /**
+     *
+     * Upload the file contents to the URL received from getUploadURLExternal method
+     *
+     * @param string $uploadURL
+     * @param string $fileContents
+     * @return bool
+     */
     public function sendFile(string $uploadURL, string $fileContents): bool
     {
         try {
@@ -111,6 +127,15 @@ public function sendFile(string $uploadURL, string $fileContents): bool
         return strtolower($response) === ('ok - ' . strlen($fileContents));
     }
 
+
+    /**
+     *
+     * Post the uploaded file to a channel
+     *
+     * @param string $channel
+     * @param string $subject
+     * @return bool
+     */
     public function completeUploadExternal(string $channel, string $subject): bool
     {
         try {
@@ -135,8 +160,21 @@ public function completeUploadExternal(string $channel, string $subject): bool
         return !empty($data['ok']);
     }
 
+    /**
+     *
+     * Send a text message to a Slack channel
+     *
+     * @param string $message
+     * @param string $channel
+     * @return bool
+     */
     public function sendMessage(string $message, string $channel): bool
     {
+        if (empty($message) || empty($channel)) {
+            $this->logger->debug('Empty message or channel for sending message');
+            return false;
+        }
+
         try {
             $response = $this->sendHttpRequest(
                 self::SLACK_POST_MESSAGE_URL,
@@ -158,6 +196,18 @@ public function sendMessage(string $message, string $channel): bool
         return !empty($data['ok']);
     }
 
+    /**
+     *
+     * Wrapper to send HTTP request
+     *
+     * @param string $url
+     * @param int $timeout
+     * @param array $requestBody
+     * @param array $additionalHeaders
+     * @param $requestBodyAsString
+     * @return array|bool|int[]|string
+     * @throws \Exception
+     */
     public function sendHttpRequest(string $url, int $timeout, array $requestBody, array $additionalHeaders = [], $requestBodyAsString = false)
     {
         if ($requestBodyAsString && !empty($requestBody[0])) {
diff --git a/lang/en.json b/lang/en.json
index f3e19b0..5d1c6dc 100644
--- a/lang/en.json
+++ b/lang/en.json
@@ -7,6 +7,7 @@
     "OauthTokenSettingDescription": "Enter your Slack OAuth Token generated from your Slack. %1$sLearn more%2$s.",
     "PleaseFindYourReport": "Here is your %1$s report for %2$s",
     "SlackChannelIdRequiredErrorMessage": "Slack Channel ID cannot be empty.",
+    "SlackChannelIdInvalidErrorMessage": "Invalid Slack Channel ID, only alphanumeric values are allowed.",
     "SlackChannel": "Slack Channel",
     "SlackEnterYourSlackChannelIdHelpText": "Enter the Slack Channel ID of the channel that will receive these reports. To find the ID, go to Slack and open the channel details > About tab. %1$sLearn more%2$s",
     "SlackAlertContent": "%1$s has been triggered for website %2$s as the metric %3$s in report %4$s %5$s."
diff --git a/tests/Integration/CustomAlertsApiTest.php b/tests/Integration/CustomAlertsApiTest.php
index 19acdec..312c72f 100644
--- a/tests/Integration/CustomAlertsApiTest.php
+++ b/tests/Integration/CustomAlertsApiTest.php
@@ -9,6 +9,8 @@
 
 namespace Piwik\Plugins\Slack\tests;
 
+use Piwik\Container\StaticContainer;
+use Piwik\Plugins\Slack\SystemSettings;
 use Piwik\Tests\Framework\Fixture;
 use Piwik\Tests\Framework\TestCase\IntegrationTestCase;
 use Piwik\Tests\Framework\TestingEnvironmentManipulator;
@@ -43,6 +45,20 @@ public function setUp(): void
         $this->idSite = Fixture::createWebsite('2012-08-09 11:22:33');
     }
 
+    public function testAddAlertShouldThrowExceptionIfSlackOauthTokenNotSet()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_OauthTokenRequiredErrorMessage');
+        $this->addAlert('', false);
+    }
+
+    public function testAddAlertShouldThrowExceptionIfSlackChannelIdNotEmptyButOauthTokenNotSet()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_OauthTokenRequiredErrorMessage');
+        $this->addAlert('channelID', false);
+    }
+
     public function testAddAlertShouldThrowExceptionIfEmptySlackChannelId()
     {
         $this->expectException(\Exception::class);
@@ -50,6 +66,20 @@ public function testAddAlertShouldThrowExceptionIfEmptySlackChannelId()
         $this->addAlert();
     }
 
+    public function testAddAlertShouldThrowExceptionIfInvalidSlackChannelId()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdInvalidErrorMessage');
+        $this->addAlert('ChanneldId1@123');
+    }
+
+    public function testAddAlertShouldThrowExceptionIfInvalidSlackChannelId2()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdInvalidErrorMessage');
+        $this->addAlert('ChannelID1,ChannelID2');
+    }
+
     public function testAddAlertSuccess()
     {
         $id = $this->addAlert($slackChannelId = 'channelID');
@@ -76,8 +106,13 @@ public function testUpdateAlertSuccess()
         $this->assertEquals('channelIDNew', $alert['slack_channel_id']);
     }
 
-    private function addAlert($slackChannelId = '')
+    private function addAlert($slackChannelId = '', $createToken = true)
     {
+        if ($createToken) {
+            $settings = StaticContainer::get(SystemSettings::class);
+            $settings->slackOauthToken->setValue('test123');
+        }
+
         return $this->api->addAlert(
             'Test Slack and Email',
             $this->idSite,
diff --git a/tests/Integration/SlackTest.php b/tests/Integration/SlackTest.php
index 95258c3..c949d43 100644
--- a/tests/Integration/SlackTest.php
+++ b/tests/Integration/SlackTest.php
@@ -10,6 +10,7 @@
 namespace Piwik\Plugins\Slack\tests;
 
 use Piwik\Container\StaticContainer;
+use Piwik\Piwik;
 use Piwik\Plugins\ScheduledReports\API;
 use Piwik\Plugins\ScheduledReports\ScheduledReports;
 use Piwik\Plugins\Slack\Slack;
@@ -113,6 +114,72 @@ public function getAlertData()
         ];
     }
 
+    public function testValidateReportParametersSlackTokenNotSetShouldThrowOauthException()
+    {
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_OauthTokenRequiredErrorMessage');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+    }
+
+    public function testValidateReportParametersSlackTokenNotSetShouldThrowSlackChannelIdEmptyException()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdRequiredErrorMessage');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+    }
+
+    public function testValidateReportParametersSlackTokenNotSetShouldThrowSlackChannelIdEmptyException2()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdRequiredErrorMessage');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY, Slack::SLACK_CHANNEL_ID_PARAMETER => ''];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+    }
+
+    public function testValidateReportParametersSlackTokenNotSetShouldThrowSlackChannelIdInvalidException()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdInvalidErrorMessage');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY, Slack::SLACK_CHANNEL_ID_PARAMETER => 'test123@11'];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+    }
+
+    public function testValidateReportParametersSlackTokenNotSetShouldThrowSlackChannelIdInvalidException2()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $this->expectException(\Exception::class);
+        $this->expectExceptionMessage('Slack_SlackChannelIdInvalidErrorMessage');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY, Slack::SLACK_CHANNEL_ID_PARAMETER => 'test123,Demo@11'];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+    }
+
+    public function testValidateReportParametersSlackTokenShouldNotThrowAnyException()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY, Slack::SLACK_CHANNEL_ID_PARAMETER => 'test123'];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+        $this->assertNotEmpty($parameters);
+    }
+
+    public function testValidateReportParametersSlackTokenShouldNotThrowAnyException2()
+    {
+        $settings = StaticContainer::get(SystemSettings::class);
+        $settings->slackOauthToken->setValue('test123');
+        $parameters = [ScheduledReports::DISPLAY_FORMAT_PARAMETER => ScheduledReports::DISPLAY_FORMAT_GRAPHS_ONLY, Slack::SLACK_CHANNEL_ID_PARAMETER => 'test123,dEmoA,abcd123'];
+        Piwik::postEvent('ScheduledReports.validateReportParameters', [&$parameters, 'slack']);
+        $this->assertNotEmpty($parameters);
+    }
+
     private function assertHasReport($login, $idSite)
     {
         $report = $this->getReport($login, $idSite);