diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
new file mode 100644
index 0000000..776c4f6
--- /dev/null
+++ b/.github/workflows/ci.yaml
@@ -0,0 +1,68 @@
+name: Full CI process
+on:
+    push:
+        branches:
+            - master
+    pull_request:
+        branches:
+            - master
+
+jobs:
+    test:
+        name: PHP ${{ matrix.php-versions }}
+        runs-on: ubuntu-18.04
+        strategy:
+            fail-fast: false
+            matrix:
+                php-versions: ['7.1', '7.2', '7.3', '7.4', '8.0']
+
+        steps:
+            # —— Setup Github actions 🐙 —————————————————————————————————————————————
+            # https://github.com/actions/checkout (official)
+            -
+                name: Checkout
+                uses: actions/checkout@v2
+
+            # https://github.com/shivammathur/setup-php (community)
+            -
+                name: Setup PHP and composer with shivammathur/setup-php
+                uses: shivammathur/setup-php@v2
+                with:
+                    php-version: ${{ matrix.php-versions }}
+                    coverage: none
+
+            # —— Composer 🧙‍️ —————————————————————————————————————————————————————————
+            -
+                name: Install Composer dependencies
+                run: composer update --no-progress --no-interaction --no-suggest --optimize-autoloader --ansi
+
+            ## —— Tests ✅ ———————————————————————————————————————————————————————————
+            -
+                name: Run Tests
+                run: vendor/bin/phpunit --disallow-test-output --verbose
+    phpstan:
+        name: PHPStan
+        runs-on: ubuntu-latest
+        strategy:
+            fail-fast: false
+        steps:
+            -
+                name: Checkout
+                uses: actions/checkout@v2
+
+            # https://github.com/shivammathur/setup-php (community)
+            -
+                name: Setup PHP and composer with shivammathur/setup-php
+                uses: shivammathur/setup-php@v2
+                with:
+                    php-version: '7.4'
+                    coverage: none
+
+            # —— Composer 🧙‍️ —————————————————————————————————————————————————————————
+            -
+                name: Install Composer dependencies
+                run: composer update --no-progress --no-interaction --no-suggest --optimize-autoloader --ansi
+
+            -
+                name: Run PHPStan
+                run: vendor/bin/phpstan analyse
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 9be9efc..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,27 +0,0 @@
-language: php
-
-sudo: false
-
-branches:
-    only:
-        - master
-
-matrix:
-    include:
-        - php: '7.1'
-        - php: '7.2'
-
-cache:
-    directories:
-        - $HOME/.composer/cache
-
-before_install:
-    - phpenv config-rm xdebug.ini || echo "xdebug not available"
-    - export PATH="$PATH:$HOME/.composer/vendor/bin"
-
-install:
-    - composer install --no-progress --no-suggest --ansi
-
-script:
-    - ./vendor/bin/phpunit --disallow-test-output --verbose
-    - ./vendor/bin/phpstan analyse
diff --git a/composer.json b/composer.json
index 1ab0fb4..8ce597c 100644
--- a/composer.json
+++ b/composer.json
@@ -10,13 +10,13 @@
         }
     ],
     "require": {
-        "php": "^7.1"
+        "php": "^7.1|^8.0"
     },
      "require-dev": {
-         "phpunit/phpunit": "^7.3.2",
-         "phpstan/phpstan": "^0.10.3",
-         "phpstan/phpstan-phpunit": "^0.10",
-         "symfony/phpunit-bridge": "^4.1"
+         "phpunit/phpunit": "^7.3.2|^8.5.12",
+         "phpstan/phpstan": "^0.12.33",
+         "phpstan/phpstan-phpunit": "^0.12.13",
+         "symfony/phpunit-bridge": "^5.2"
      },
     "autoload": {
         "psr-4": {
diff --git a/phpstan.neon b/phpstan.neon
index 1ed8567..c05fef4 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -1,10 +1,9 @@
+includes:
+    - vendor/phpstan/phpstan-phpunit/extension.neon
+
 parameters:
     level: 7
     paths:
         - src
         - tests
-    autoload_files:
-        - vendor/autoload.php
     ignoreErrors:
-    includes:
-        - vendor/phpstan/phpstan-phpunit/extension.neon
diff --git a/src/ContinuesVersionsValidator.php b/src/ContinuesVersionsValidator.php
index f34f350..d4868cc 100644
--- a/src/ContinuesVersionsValidator.php
+++ b/src/ContinuesVersionsValidator.php
@@ -106,7 +106,10 @@ private function computePossibleVersionsFromLastExisting(): void
         $this->possibleVersions = $version->getNextVersionCandidates();
     }
 
-    private function getLastArrayIndex(array $array)
+    /**
+     * @param array<int, mixed> $array
+     */
+    private function getLastArrayIndex(array $array): int
     {
         end($array);
 
diff --git a/src/Version.php b/src/Version.php
index 2873a6c..7220c3e 100644
--- a/src/Version.php
+++ b/src/Version.php
@@ -50,7 +50,7 @@ final class Version
     /**
      * Higher means more stable.
      *
-     * @var int[]
+     * @var array<string,int>
      */
     private static $stabilityIndexes = [
         'alpha' => self::STABILITY_ALPHA,
@@ -81,7 +81,7 @@ private function __construct(int $major, int $minor, int $patch, int $stability,
                 $this->major,
                 $this->minor,
                 $this->patch,
-                strtoupper(array_search($this->stability, self::$stabilityIndexes, true)),
+                strtoupper(array_search($this->stability, self::$stabilityIndexes, true)), /** @phpstan-ignore-line */
                 $this->metaver
             );
         } else {
diff --git a/tests/ContinuesVersionsValidatorTest.php b/tests/ContinuesVersionsValidatorTest.php
index a59a14a..2efb024 100644
--- a/tests/ContinuesVersionsValidatorTest.php
+++ b/tests/ContinuesVersionsValidatorTest.php
@@ -19,6 +19,9 @@
 
 class ContinuesVersionsValidatorTest extends TestCase
 {
+    /**
+     * @return array<int, string[]>
+     */
     public function provideInitialContinuesVersions(): iterable
     {
         yield ['0.1.0'];
@@ -31,7 +34,7 @@ public function provideInitialContinuesVersions(): iterable
      * @test
      * @dataProvider provideInitialContinuesVersions
      */
-    public function it_accepts_a_continues_version_with_no_pre_existing(string $new)
+    public function it_accepts_a_continues_version_with_no_pre_existing(string $new): void
     {
         $validator = new ContinuesVersionsValidator();
 
@@ -47,6 +50,9 @@ public function it_accepts_a_continues_version_with_no_pre_existing(string $new)
         );
     }
 
+    /**
+     * @return array<string, array<int, string[]|string>>
+     */
     public function provideContinuesVersions(): iterable
     {
         yield 'unstable #1' => ['0.3', ['0.2', '0.1'], ['0.2.1', '0.3', '1.0-BETA1', '1.0']];
@@ -63,8 +69,11 @@ public function provideContinuesVersions(): iterable
     /**
      * @test
      * @dataProvider provideContinuesVersions
+     *
+     * @param array<int, string> $existing
+     * @param array<int, string> $possible
      */
-    public function it_accepts_a_continues_version(string $new, array $existing, array $possible)
+    public function it_accepts_a_continues_version(string $new, array $existing, array $possible): void
     {
         $validator = new ContinuesVersionsValidator(...$this->createVersions($existing));
 
@@ -72,6 +81,11 @@ public function it_accepts_a_continues_version(string $new, array $existing, arr
         self::assertEquals($this->createVersions($possible), array_merge([], $validator->getPossibleVersions()));
     }
 
+    /**
+     * @param array<int, string> $existing
+     *
+     * @return array<int, Version>
+     */
     private function createVersions(array $existing): array
     {
         return array_map(
@@ -82,6 +96,9 @@ function (string $version) {
         );
     }
 
+    /**
+     * @return array<int, string[]>
+     */
     public function provideNotInitialContinuesVersions(): iterable
     {
         yield ['0.2.0'];
@@ -95,7 +112,7 @@ public function provideNotInitialContinuesVersions(): iterable
      * @test
      * @dataProvider provideNotInitialContinuesVersions
      */
-    public function it_rejects_non_continues_version_with_no_pre_existing(string $new)
+    public function it_rejects_non_continues_version_with_no_pre_existing(string $new): void
     {
         $validator = new ContinuesVersionsValidator();
 
@@ -111,6 +128,9 @@ public function it_rejects_non_continues_version_with_no_pre_existing(string $ne
         );
     }
 
+    /**
+     * @return array<string, array<int, string[]|string>>
+     */
     public function provideNonContinuesVersions(): iterable
     {
         yield 'unstable #1' => ['0.5', ['0.2', '0.1'], ['0.2.1', '0.3', '1.0-BETA1', '1.0']];
@@ -127,8 +147,11 @@ public function provideNonContinuesVersions(): iterable
     /**
      * @test
      * @dataProvider provideNonContinuesVersions
+     *
+     * @param array<int, string> $existing
+     * @param array<int, string> $possible
      */
-    public function it_rejects_non_continues_version(string $new, array $existing, array $possible)
+    public function it_rejects_non_continues_version(string $new, array $existing, array $possible): void
     {
         $validator = new ContinuesVersionsValidator(...$this->createVersions($existing));
 
diff --git a/tests/VersionTest.php b/tests/VersionTest.php
index fc57d22..90bfca9 100644
--- a/tests/VersionTest.php
+++ b/tests/VersionTest.php
@@ -19,7 +19,7 @@
 class VersionTest extends TestCase
 {
     /** @test */
-    public function it_creates_from_full_string()
+    public function it_creates_from_full_string(): void
     {
         $version = Version::fromString('1.0.0-beta-5');
 
@@ -33,7 +33,7 @@ public function it_creates_from_full_string()
     }
 
     /** @test */
-    public function it_creates_with_explicit_stable()
+    public function it_creates_with_explicit_stable(): void
     {
         $version = Version::fromString('1.0.0-stable');
 
@@ -47,7 +47,7 @@ public function it_creates_with_explicit_stable()
     }
 
     /** @test */
-    public function it_creates_without_patch()
+    public function it_creates_without_patch(): void
     {
         $version = Version::fromString('1.0');
 
@@ -60,6 +60,9 @@ public function it_creates_without_patch()
         self::assertEquals('1.0.0', (string) $version);
     }
 
+    /**
+     * @return array<string,string[]>
+     */
     public function provideValidFormats(): array
     {
         return [
@@ -77,7 +80,7 @@ public function provideValidFormats(): array
      * @test
      * @dataProvider provideValidFormats
      */
-    public function it_supports_various_formats(string $version, string $expectedOutput)
+    public function it_supports_various_formats(string $version, string $expectedOutput): void
     {
         $version = Version::fromString($version);
 
@@ -85,7 +88,7 @@ public function it_supports_various_formats(string $version, string $expectedOut
     }
 
     /** @test */
-    public function it_compares_two_versions_are_equal()
+    public function it_compares_two_versions_are_equal(): void
     {
         $version = Version::fromString('1.0.0-beta-5');
         $version2 = Version::fromString('1.0.0-beta5');
@@ -96,7 +99,7 @@ public function it_compares_two_versions_are_equal()
     }
 
     /** @test */
-    public function it_fails_for_invalid_format()
+    public function it_fails_for_invalid_format(): void
     {
         $this->expectException('InvalidArgumentException');
         $this->expectExceptionMessage('Unable to parse version "1.0.0-WAT"');
@@ -105,7 +108,7 @@ public function it_fails_for_invalid_format()
     }
 
     /** @test */
-    public function it_fails_with_stable_plus_metaver()
+    public function it_fails_with_stable_plus_metaver(): void
     {
         $this->expectException('InvalidArgumentException');
         $this->expectExceptionMessage('Meta version of the stability flag cannot be set for stable.');
@@ -113,6 +116,9 @@ public function it_fails_with_stable_plus_metaver()
         Version::fromString('1.0.0-stable-5');
     }
 
+    /**
+     * @return array<string,array<int, array<int, string>|string>>>
+     */
     public function provideExpectedNextVersionCandidates(): array
     {
         return [
@@ -132,8 +138,10 @@ public function provideExpectedNextVersionCandidates(): array
     /**
      * @test
      * @dataProvider provideExpectedNextVersionCandidates
+     *
+     * @param array<int, string> $expected
      */
-    public function it_provides_next_version_candidates($current, $expected)
+    public function it_provides_next_version_candidates(string $current, array $expected): void
     {
         $candidates = Version::fromString($current)->getNextVersionCandidates();
         $expected = array_map([Version::class, 'fromString'], $expected);
@@ -141,6 +149,9 @@ public function it_provides_next_version_candidates($current, $expected)
         self::assertEquals($expected, $candidates);
     }
 
+    /**
+     * @return array<string,string[]>
+     */
     public function provideExpectedIncreasedVersion(): array
     {
         return [
@@ -199,13 +210,13 @@ public function provideExpectedIncreasedVersion(): array
      * @test
      * @dataProvider provideExpectedIncreasedVersion
      */
-    public function it_increases_to_next_version(string $current, string $expected, $stability)
+    public function it_increases_to_next_version(string $current, string $expected, string $stability): void
     {
         self::assertEquals(Version::fromString($expected), Version::fromString($current)->getNextIncreaseOf($stability));
     }
 
     /** @test */
-    public function it_cannot_increases_for_unsupported()
+    public function it_cannot_increases_for_unsupported(): void
     {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Unknown stability "next-stable", accepts "alpha", "beta", "rc", "stable", "major", "next", "minor", "patch".');