diff --git a/composer.json b/composer.json
index 5b3569c..c0662b3 100644
--- a/composer.json
+++ b/composer.json
@@ -7,9 +7,9 @@
         "psr-4": {"Sil\\PhpEnv\\": "src/"}
     },
     "require": {
-        "php": "^7.4 || ^8.0"
+        "php": "^8.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.0"
+        "phpunit/phpunit": "^12.0"
     }
 }
diff --git a/tests/phpunit.xml b/tests/phpunit.xml
index 0cfbac9..a3bdeb5 100644
--- a/tests/phpunit.xml
+++ b/tests/phpunit.xml
@@ -1,8 +1,5 @@
 <phpunit bootstrap="bootstrap.php"
          colors="false"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
          processIsolation="true"
          stopOnFailure="false">
 
diff --git a/tests/unit/EnvTest.php b/tests/unit/EnvTest.php
index 7630dfb..6326fa1 100644
--- a/tests/unit/EnvTest.php
+++ b/tests/unit/EnvTest.php
@@ -1,4 +1,5 @@
 <?php
+
 namespace Sil\PhpEnv\tests;
 
 use PHPUnit\Framework\TestCase;
@@ -28,6 +29,10 @@ protected function putEnv($setting)
                 . 'test: "' . $setting . '"'
             );
         }
+        list ($variable, $value) = explode('=', $setting);
+        $variable = trim($variable);
+        $value = trim($value);
+        $_ENV[$variable] = $value;
     }
     
     public function testGet_notFoundNull()
@@ -40,7 +45,7 @@ public function testGet_notFoundNull()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_emptyString()
@@ -54,7 +59,7 @@ public function testGet_emptyString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame(
+        self::assertSame(
             $expected,
             $actual,
             'Expected to get the default value if only whitespace was found.'
@@ -72,7 +77,7 @@ public function testGet_spacesString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame(
+        self::assertSame(
             $expected,
             $actual,
             'Expected to get the default value if only whitespace was found.'
@@ -90,7 +95,7 @@ public function testGet_whiteSpaceString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_false()
@@ -104,7 +109,7 @@ public function testGet_false()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_falseTitlecase()
@@ -118,7 +123,7 @@ public function testGet_falseTitlecase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_falseUppercase()
@@ -132,7 +137,7 @@ public function testGet_falseUppercase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_nonEmptyLowercaseString()
@@ -146,7 +151,7 @@ public function testGet_nonEmptyLowercaseString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_nonEmptyMixedCaseString()
@@ -160,7 +165,7 @@ public function testGet_nonEmptyMixedCaseString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_nonEmptyUppercaseString()
@@ -174,7 +179,7 @@ public function testGet_nonEmptyUppercaseString()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_notSetHasDefault()
@@ -188,7 +193,7 @@ public function testGet_notSetHasDefault()
         $actual = Env::get($varname, $default);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_notSetNoDefault()
@@ -201,7 +206,7 @@ public function testGet_notSetNoDefault()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_null()
@@ -215,7 +220,7 @@ public function testGet_null()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_nullTitlecase()
@@ -229,7 +234,7 @@ public function testGet_nullTitlecase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_nullUppercase()
@@ -243,7 +248,7 @@ public function testGet_nullUppercase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_true()
@@ -257,7 +262,7 @@ public function testGet_true()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_trueTitlecase()
@@ -271,7 +276,7 @@ public function testGet_trueTitlecase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGet_trueUppercase()
@@ -285,7 +290,7 @@ public function testGet_trueUppercase()
         $actual = Env::get($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testRequireEnv_exists()
@@ -299,7 +304,7 @@ public function testRequireEnv_exists()
         $actual = Env::requireEnv($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testRequireEnv_notfound()
@@ -340,7 +345,7 @@ public function testGetArray_notFound()
         $actual = Env::getArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_existsButNoValue()
@@ -354,7 +359,7 @@ public function testGetArray_existsButNoValue()
         $actual = Env::getArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_existsButNoValueHasDefault()
@@ -369,7 +374,7 @@ public function testGetArray_existsButNoValueHasDefault()
         $actual = Env::getArray($varname, $default);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_1exists()
@@ -383,7 +388,7 @@ public function testGetArray_1exists()
         $actual = Env::getArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_multiExists()
@@ -397,7 +402,7 @@ public function testGetArray_multiExists()
         $actual = Env::getArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_multiEmptyExists()
@@ -411,7 +416,7 @@ public function testGetArray_multiEmptyExists()
         $actual = Env::getArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_existsWithDefault()
@@ -426,7 +431,7 @@ public function testGetArray_existsWithDefault()
         $actual = Env::getArray($varname, $default);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_notFoundWithDefault()
@@ -440,7 +445,7 @@ public function testGetArray_notFoundWithDefault()
         $actual = Env::getArray($varname, $default);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArray_existsWithInvalidDefaultType()
@@ -481,7 +486,7 @@ public function testGetArray_notFoundWithNullDefault()
         $actual = Env::getArray($varname, null);
 
         // Assert
-        $this->assertNull($actual);
+        self::assertNull($actual);
     }
     
     public function testGetArrayFromPrefix_multiple()
@@ -500,7 +505,7 @@ public function testGetArrayFromPrefix_multiple()
             'fourthOne' => null,
             'andAFifth' => '123',
         ];
-        
+
         // Act
         try {
             $actual = Env::getArrayFromPrefix($prefix);
@@ -509,7 +514,7 @@ public function testGetArrayFromPrefix_multiple()
         }
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArrayFromPrefix_notFound()
@@ -526,7 +531,7 @@ public function testGetArrayFromPrefix_notFound()
         }
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testGetArrayFromPrefix_one()
@@ -546,7 +551,7 @@ public function testGetArrayFromPrefix_one()
         }
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testRequireArray_exists()
@@ -560,7 +565,7 @@ public function testRequireArray_exists()
         $actual = Env::requireArray($varname);
 
         // Assert
-        $this->assertSame($expected, $actual);
+        self::assertSame($expected, $actual);
     }
     
     public function testRequireArray_notfound()