diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index ffd1f3433..6da8f1ead 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -10,7 +10,9 @@ on:
 
 env:
   COMPOSER_FLAGS: "--ansi --no-interaction --no-progress --no-suggest --prefer-dist"
-  SYMFONY_PHPUNIT_VERSION: ""
+  COMPOSER_UPDATE_FLAGS: ""
+  SYMFONY_PHPUNIT_VERSION: "8.3"
+  SYMFONY_PHPUNIT_REMOVE_RETURN_TYPEHINT: "1"
 
 jobs:
   tests:
@@ -68,6 +70,30 @@ jobs:
       - name: "Checkout"
         uses: "actions/checkout@v2"
 
+      - name: "Install PHP 7.4 to prepare nightly builds"
+        if: "matrix.php-version == '8.0'"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          extensions: "intl"
+          ini-values: "memory_limit=-1, phar.readonly=0"
+          php-version: "7.4"
+
+      - name: "Choose PHPUnit version"
+        if: "!startsWith(matrix.os, 'windows')"
+        run: |
+          if [ "${{ matrix.php-version }}" = "5.3" ] || [ "${{ matrix.php-version }}" = "5.4" ] || [ "${{ matrix.php-version }}" = "5.5" ]; then
+            echo "::set-env name=SYMFONY_PHPUNIT_VERSION::4.8";
+          elif [ "${{ matrix.php-version }}" = "5.6" ]; then
+            echo "::set-env name=SYMFONY_PHPUNIT_VERSION::5.7";
+          elif [ "${{ matrix.php-version }}" = "7.0" ]; then
+            echo "::set-env name=SYMFONY_PHPUNIT_VERSION::6.5";
+          elif [ "${{ matrix.php-version }}" = "7.1" ]; then
+            echo "::set-env name=SYMFONY_PHPUNIT_VERSION::7.5";
+          else
+            echo "::set-env name=SYMFONY_PHPUNIT_VERSION::8.3";
+          fi
+
       - name: "Install PHP"
         uses: "shivammathur/setup-php@v2"
         with:
@@ -87,28 +113,29 @@ jobs:
           key: "php-${{ matrix.php-version }}-symfony-php-unit-version-${{ env.SYMFONY_PHPUNIT_VERSION }}-${{ hashFiles('**/composer.lock') }}"
           restore-keys: "php-${{ matrix.php-version }}-symfony-php-unit-version-${{ env.SYMFONY_PHPUNIT_VERSION }}"
 
-      - name: "Install highest dependencies from composer.json using composer binary provided by system"
-        if: "matrix.dependencies == 'highest'"
-        run: "composer config platform --unset && composer update ${{ env.COMPOSER_FLAGS }}"
+      - name: "Handle lowest dependencies update"
+        if: "contains(matrix.dependencies, 'lowest')"
+        run: "echo \"::set-env name=COMPOSER_UPDATE_FLAGS::$COMPOSER_UPDATE_FLAGS --prefer-lowest\""
 
-      - name: "Install highest dependencies from composer.json using composer binary provided by system, ignoring platform requirements"
-        if: "matrix.dependencies == 'highest-ignore'"
-        run: "composer config platform --unset && composer update ${{ env.COMPOSER_FLAGS }} --ignore-platform-reqs"
+      - name: "Handle ignore-platform-reqs dependencies update"
+        if: "contains(matrix.dependencies, 'ignore')"
+        run: "echo \"::set-env name=COMPOSER_FLAGS::$COMPOSER_FLAGS --ignore-platform-reqs\""
 
-      - name: "Install lowest dependencies from composer.json using composer binary provided by system"
-        if: "matrix.dependencies == 'lowest'"
-        run: "composer update ${{ env.COMPOSER_FLAGS }} --prefer-lowest"
+      - name: "Remove platform config to get latest dependencies for current PHP version when build is not locked"
+        run: "composer config platform --unset"
 
-      - name: "Install lowest dependencies from composer.json using composer binary provided by system, ignoring platform requirements"
-        if: "matrix.dependencies == 'lowest-ignore'"
-        run: "composer update ${{ env.COMPOSER_FLAGS }} --prefer-lowest --ignore-platform-reqs"
+      - name: "Update dependencies from composer.json using composer binary provided by system"
+        if: "contains(matrix.dependencies, 'highest') || contains(matrix.dependencies, 'lowest')"
+        run: "composer update ${{ env.COMPOSER_UPDATE_FLAGS }} ${{ env.COMPOSER_FLAGS }}"
 
       - name: "Install dependencies from composer.lock using composer binary provided by system"
         if: "matrix.dependencies == 'locked'"
         run: "composer install ${{ env.COMPOSER_FLAGS }}"
 
+      - name: "Update Symfony's PHPUnitBridge to latest available for the current PHP always as it is not really a dependency of the project"
+        run: "composer update ${{ env.COMPOSER_FLAGS }} symfony/phpunit-bridge"
+
       - name: "Run install again using composer binary from source"
-        if: "matrix.dependencies != 'highest-ignore'"
         run: "bin/composer install ${{ env.COMPOSER_FLAGS }}"
 
       - name: "Validate composer.json"
@@ -117,21 +144,15 @@ jobs:
       - name: "Prepare git environment"
         run: "git config --global user.name composer && git config --global user.email composer@example.com"
 
-      - name: "Set SYMFONY_PHPUNIT_VERSION environment variable"
-        if: "matrix.php-version == '7.4'"
-        run: "echo \"::set-env name=SYMFONY_PHPUNIT_VERSION::7.5\""
-
-      - name: "Run tests"
-        if: "matrix.php-version != '8.0' && matrix.php-version != '7.3'"
-        run: "vendor/bin/simple-phpunit"
-
-      - name: "Run Complete test suite"
-        if: "matrix.php-version == '7.3'"
-        run: "vendor/bin/simple-phpunit --configuration tests/complete.phpunit.xml"
-
-      - name: "Run tests for PHP 8"
+      - name: "Pre-install PHPUnit using PHP 7.4 for PHP 8"
         if: "matrix.php-version == '8.0'"
         run: |
-          bin/composer remove --dev symfony/phpunit-bridge --ignore-platform-reqs
-          bin/composer require phpunit/phpunit:^7.5 --ignore-platform-reqs --with-dependencies
-          vendor/bin/phpunit
+          php7.4 vendor/bin/simple-phpunit install
+
+      - name: "Run tests"
+        if: "matrix.php-version != '7.3'"
+        run: "vendor/bin/simple-phpunit"
+
+      - name: "Run complete test suite on 7.3"
+        if: "matrix.php-version == '7.3'"
+        run: "vendor/bin/simple-phpunit --configuration tests/complete.phpunit.xml"
diff --git a/composer.json b/composer.json
index 415df800f..7a670ecb0 100644
--- a/composer.json
+++ b/composer.json
@@ -24,17 +24,17 @@
     "require": {
         "php": "^5.3.2 || ^7.0",
         "composer/ca-bundle": "^1.0",
-        "composer/semver": "^2.0@dev",
+        "composer/semver": "^2.1@dev",
         "composer/spdx-licenses": "^1.2",
         "composer/xdebug-handler": "^1.1",
         "justinrainbow/json-schema": "^3.0 || ^4.0 || ^5.0",
         "psr/log": "^1.0",
         "seld/jsonlint": "^1.4",
         "seld/phar-utils": "^1.0",
-        "symfony/console": "^2.7 || ^3.0 || ^4.0 || ^5.0",
-        "symfony/filesystem": "^2.7 || ^3.0 || ^4.0 || ^5.0",
-        "symfony/finder": "^2.7 || ^3.0 || ^4.0 || ^5.0",
-        "symfony/process": "^2.7 || ^3.0 || ^4.0 || ^5.0",
+        "symfony/console": "^2.8.52 || ^3.4 || ^4.4 || ^5.0",
+        "symfony/filesystem": "^2.8.52 || ^3.4 || ^4.4 || ^5.0",
+        "symfony/finder": "^2.8.52 || ^3.4 || ^4.4 || ^5.0",
+        "symfony/process": "^2.8.52 || ^3.4 || ^4.4 || ^5.0",
         "react/promise": "^1.2 || ^2.7"
     },
     "conflict": {
diff --git a/composer.lock b/composer.lock
index 4f27da9f3..f8c918820 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "a5f07d1ae8479fae25dd57b2d966cd22",
+    "content-hash": "4661f272e877e4aaaaf1cf0848b891b7",
     "packages": [
         {
             "name": "composer/ca-bundle",
@@ -83,12 +83,12 @@
             "source": {
                 "type": "git",
                 "url": "https://github.com/composer/semver.git",
-                "reference": "594e5242ff1ba3aac2f4b8401d3f1ca1d781fd89"
+                "reference": "07a3e324e654298714fcecfbb4604e3ee0c6f3bd"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/composer/semver/zipball/594e5242ff1ba3aac2f4b8401d3f1ca1d781fd89",
-                "reference": "594e5242ff1ba3aac2f4b8401d3f1ca1d781fd89",
+                "url": "https://api.github.com/repos/composer/semver/zipball/07a3e324e654298714fcecfbb4604e3ee0c6f3bd",
+                "reference": "07a3e324e654298714fcecfbb4604e3ee0c6f3bd",
                 "shasum": ""
             },
             "require": {
@@ -96,7 +96,7 @@
             },
             "require-dev": {
                 "phpstan/phpstan": "^0.12.19",
-                "phpunit/phpunit": "^4.5 || ^5.0.5 || ^7"
+                "symfony/phpunit-bridge": "^4.2 || ^5"
             },
             "type": "library",
             "extra": {
@@ -156,7 +156,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2020-05-19T14:49:33+00:00"
+            "time": "2020-05-20T08:27:54+00:00"
         },
         {
             "name": "composer/spdx-licenses",
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 728125c15..75c2f3c74 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -10,7 +10,6 @@
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          failOnRisky="true"
-         strict="false"
          processIsolation="false"
          stopOnFailure="false"
          bootstrap="tests/bootstrap.php"
diff --git a/tests/Composer/Test/IO/ConsoleIOTest.php b/tests/Composer/Test/IO/ConsoleIOTest.php
index ef5096300..1ff86170c 100644
--- a/tests/Composer/Test/IO/ConsoleIOTest.php
+++ b/tests/Composer/Test/IO/ConsoleIOTest.php
@@ -84,7 +84,7 @@ class ConsoleIOTest extends TestCase
             ->with(
                 $this->callback(function ($messages) {
                     $result = preg_match("[(.*)/(.*) First line]", $messages[0]) > 0;
-                    $result &= preg_match("[(.*)/(.*) Second line]", $messages[1]) > 0;
+                    $result = $result && preg_match("[(.*)/(.*) Second line]", $messages[1]) > 0;
 
                     return $result;
                 }),
diff --git a/tests/Composer/Test/Util/ErrorHandlerTest.php b/tests/Composer/Test/Util/ErrorHandlerTest.php
index 89cc8b4dc..ef501542e 100644
--- a/tests/Composer/Test/Util/ErrorHandlerTest.php
+++ b/tests/Composer/Test/Util/ErrorHandlerTest.php
@@ -46,7 +46,11 @@ class ErrorHandlerTest extends TestCase
      */
     public function testErrorHandlerCaptureWarning()
     {
-        $this->setExpectedException('\ErrorException', 'array_merge');
+        if (PHP_VERSION_ID >= 80000) {
+            $this->setExpectedException('TypeError', 'array_merge');
+        } else {
+            $this->setExpectedException('ErrorException', 'array_merge');
+        }
 
         array_merge(array(), 'string');
     }
diff --git a/tests/complete.phpunit.xml b/tests/complete.phpunit.xml
index 30faf6837..14b2de093 100644
--- a/tests/complete.phpunit.xml
+++ b/tests/complete.phpunit.xml
@@ -10,7 +10,6 @@
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          failOnRisky="true"
-         strict="false"
          processIsolation="false"
          stopOnFailure="false"
          bootstrap="./bootstrap.php"