diff --git a/.gitattributes b/.gitattributes
index 44ad9edd..5b6b4f25 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -6,6 +6,7 @@
 /.gitignore export-ignore
 /.travis.yml export-ignore
 /phpstan.neon.dist export-ignore
+/phpstan.tests.neon.dist export-ignore
 /phpunit.xml.dist export-ignore
 /README.md export-ignore
 /UPGRADING.md export-ignore
diff --git a/.gitignore b/.gitignore
index 7ae55bb3..5081dd65 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 composer.lock
 phpstan.neon
+phpstan.tests.neon
 phpunit.xml
 vendor
diff --git a/.travis.yml b/.travis.yml
index 3730b209..8062ee4e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -41,4 +41,6 @@ matrix:
       install: 
         - travis_retry docker run -it -w /data -v ${PWD}:/data:delegated --entrypoint composer registry.gitlab.com/grahamcampbell/php:7.4 install --no-suggest --prefer-dist -n -o
         - travis_retry docker run -it -w /data -v ${PWD}:/data:delegated --entrypoint composer registry.gitlab.com/grahamcampbell/php:7.4 bin phpstan install --no-suggest --prefer-dist -n -o
-      script: docker run -it -w /data -v ${PWD}:/data:delegated --entrypoint vendor/bin/phpstan registry.gitlab.com/grahamcampbell/php:7.4 analyse src
+      script: 
+        - docker run -it -w /data -v ${PWD}:/data:delegated --entrypoint vendor/bin/phpstan registry.gitlab.com/grahamcampbell/php:7.4 analyse src
+        - docker run -it -w /data -v ${PWD}:/data:delegated --entrypoint vendor/bin/phpstan registry.gitlab.com/grahamcampbell/php:7.4 analyse tests -c phpstan.tests.neon.dist
diff --git a/composer.json b/composer.json
index ab29a9bc..2fa9e829 100644
--- a/composer.json
+++ b/composer.json
@@ -17,7 +17,7 @@
     ],
     "require": {
         "php": "^5.5.9 || ^7.0",
-        "phpoption/phpoption": "^1.7",
+        "phpoption/phpoption": "^1.7.1",
         "symfony/polyfill-ctype": "^1.9"
     },
     "require-dev": {
@@ -29,6 +29,11 @@
             "Dotenv\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "Dotenv\\Tests\\": "tests/Dotenv/"
+        }
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "4.1-dev"
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 1c44e85a..25ec083d 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -10,3 +10,7 @@ parameters:
     - '#Method Dotenv\\Loader\\Lines::getCharPairs\(\) should return array\(array\(string, string\|null\)\) but returns array\<int, mixed\>.#'
     - '#Unable to resolve the template type S in call to method PhpOption\\Option<mixed>::flatMap\(\)#'
     - '#Method Dotenv\\Loader\\Parser::processChar\(\) should return Dotenv\\Result\\Result<array<int, bool\|int\|string>, string> but returns Dotenv\\Result\\Result<array<int, [a-z\|\,]+>, mixed>.#'
+    - '#Parameter \#1 \$callable of method PhpOption\\Option<Dotenv\\Loader\\Value|null>::map\(\) expects callable\(Dotenv\\Loader\\Value\|null\): mixed, Closure\(Dotenv\\Loader\\Value\): mixed given.#'
+    - '#Parameter \#1 \$callable of method PhpOption\\Option<array\|null>::[a-z]+\(\) expects callable\(array\|null\): [a-z]+, Closure\(array\): mixed given.#'                                                                          
+    - '#Method Dotenv\\Repository\\Adapter\\PutenvAdapter::get\(\) should return PhpOption\\Option<string> but returns PhpOption\\Option<bool\|string>.#'
+    - '#Method Dotenv\\Store\\File\\Reader::readFromFile\(\) should return PhpOption\\Option<string> but returns PhpOption\\Option<bool\|string>.#'
diff --git a/phpstan.tests.neon.dist b/phpstan.tests.neon.dist
new file mode 100644
index 00000000..6318d011
--- /dev/null
+++ b/phpstan.tests.neon.dist
@@ -0,0 +1,4 @@
+parameters:
+  level: 5
+  ignoreErrors:
+    - '#Parameter \#1 \$name of method Dotenv\\Repository\\RepositoryInterface::[a-z]+\(\) expects string, [a-z]+ given.#'
diff --git a/tests/Dotenv/DotenvTest.php b/tests/Dotenv/DotenvTest.php
index 9f239032..4cdb5902 100644
--- a/tests/Dotenv/DotenvTest.php
+++ b/tests/Dotenv/DotenvTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Dotenv;
 use Dotenv\Loader\Loader;
 use Dotenv\Repository\RepositoryBuilder;
diff --git a/tests/Dotenv/LinesTest.php b/tests/Dotenv/LinesTest.php
index a348a45a..495efce4 100644
--- a/tests/Dotenv/LinesTest.php
+++ b/tests/Dotenv/LinesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Loader\Lines;
 use PHPUnit\Framework\TestCase;
 
diff --git a/tests/Dotenv/LoaderTest.php b/tests/Dotenv/LoaderTest.php
index 8c541824..4c295dae 100644
--- a/tests/Dotenv/LoaderTest.php
+++ b/tests/Dotenv/LoaderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Loader\Loader;
 use Dotenv\Repository\Adapter\ArrayAdapter;
 use Dotenv\Repository\Adapter\EnvConstAdapter;
diff --git a/tests/Dotenv/ParserTest.php b/tests/Dotenv/ParserTest.php
index 7bae5d8a..5887984c 100644
--- a/tests/Dotenv/ParserTest.php
+++ b/tests/Dotenv/ParserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Loader\Parser;
 use PHPUnit\Framework\TestCase;
 
diff --git a/tests/Dotenv/RepositoryTest.php b/tests/Dotenv/RepositoryTest.php
index 9a959c3f..e5818e1c 100644
--- a/tests/Dotenv/RepositoryTest.php
+++ b/tests/Dotenv/RepositoryTest.php
@@ -1,6 +1,7 @@
-
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Dotenv;
 use Dotenv\Repository\Adapter\ArrayAdapter;
 use Dotenv\Repository\RepositoryBuilder;
diff --git a/tests/Dotenv/ResultTest.php b/tests/Dotenv/ResultTest.php
index 20309e9e..854ae763 100644
--- a/tests/Dotenv/ResultTest.php
+++ b/tests/Dotenv/ResultTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Result\Error;
 use Dotenv\Result\Success;
 use PHPUnit\Framework\TestCase;
diff --git a/tests/Dotenv/StoreTest.php b/tests/Dotenv/StoreTest.php
index f746fa43..0dfb1b90 100644
--- a/tests/Dotenv/StoreTest.php
+++ b/tests/Dotenv/StoreTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Store\File\Paths;
 use Dotenv\Store\File\Reader;
 use Dotenv\Store\StoreBuilder;
diff --git a/tests/Dotenv/ValidatorTest.php b/tests/Dotenv/ValidatorTest.php
index 0cb841d4..55ef42df 100644
--- a/tests/Dotenv/ValidatorTest.php
+++ b/tests/Dotenv/ValidatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+namespace Dotenv\Tests;
+
 use Dotenv\Dotenv;
 use PHPUnit\Framework\TestCase;
 
diff --git a/vendor-bin/phpstan/composer.json b/vendor-bin/phpstan/composer.json
index 4090b223..4c238994 100644
--- a/vendor-bin/phpstan/composer.json
+++ b/vendor-bin/phpstan/composer.json
@@ -1,5 +1,5 @@
 {
     "require": {
-        "phpstan/phpstan": "^0.12.2"
+        "phpstan/phpstan": "^0.12.3"
     }
 }