diff --git a/tests/unit/PseudoTypes/ArrayKeyTest.php b/tests/unit/PseudoTypes/ArrayKeyTest.php
index c8ba5d8..21cefad 100644
--- a/tests/unit/PseudoTypes/ArrayKeyTest.php
+++ b/tests/unit/PseudoTypes/ArrayKeyTest.php
@@ -13,13 +13,21 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Integer;
 use phpDocumentor\Reflection\Types\String_;
 use PHPUnit\Framework\TestCase;
 
 final class ArrayKeyTest extends TestCase
 {
-    public function testArrayKeyCanBeConstructedAndStringifiedCorrectly(): void
+    public function testCreate(): void
+    {
+        $type = new ArrayKey();
+
+        $this->assertEquals(new Compound([new String_(), new Integer()]), $type->underlyingType());
+    }
+
+    public function testToString(): void
     {
         $this->assertSame('array-key', (string) (new ArrayKey()));
     }
diff --git a/tests/unit/PseudoTypes/ArrayShapeItemTest.php b/tests/unit/PseudoTypes/ArrayShapeItemTest.php
new file mode 100644
index 0000000..4bfd180
--- /dev/null
+++ b/tests/unit/PseudoTypes/ArrayShapeItemTest.php
@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use PHPUnit\Framework\TestCase;
+
+class ArrayShapeItemTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $key = 'abc';
+        $value = new IntegerValue(100);
+        $item = new ArrayShapeItem($key, $value, true);
+
+        $this->assertSame($key, $item->getKey());
+        $this->assertSame($value, $item->getValue());
+        $this->assertTrue($item->isOptional());
+    }
+}
diff --git a/tests/unit/PseudoTypes/ArrayShapeTest.php b/tests/unit/PseudoTypes/ArrayShapeTest.php
index 14f3af3..47488b0 100644
--- a/tests/unit/PseudoTypes/ArrayShapeTest.php
+++ b/tests/unit/PseudoTypes/ArrayShapeTest.php
@@ -4,11 +4,13 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Array_;
+use phpDocumentor\Reflection\Types\Mixed_;
 use PHPUnit\Framework\TestCase;
 
 class ArrayShapeTest extends TestCase
 {
-    public function testExposeItems(): void
+    public function testCreate(): void
     {
         $item1 = new ArrayShapeItem('foo', new True_(), false);
         $item2 = new ArrayShapeItem('bar', new False_(), true);
@@ -16,6 +18,7 @@ public function testExposeItems(): void
         $arrayShape = new ArrayShape($item1, $item2);
 
         $this->assertSame([$item1, $item2], $arrayShape->getItems());
+        $this->assertEquals(new Array_(new Mixed_(), new ArrayKey()), $arrayShape->underlyingType());
     }
 
     /**
diff --git a/tests/unit/PseudoTypes/CallableStringTest.php b/tests/unit/PseudoTypes/CallableStringTest.php
new file mode 100644
index 0000000..5134b5a
--- /dev/null
+++ b/tests/unit/PseudoTypes/CallableStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class CallableStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new CallableString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('callable-string', (string) (new CallableString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/ClassStringTest.php b/tests/unit/PseudoTypes/ClassStringTest.php
index fe5cbe2..3e578c2 100644
--- a/tests/unit/PseudoTypes/ClassStringTest.php
+++ b/tests/unit/PseudoTypes/ClassStringTest.php
@@ -16,14 +16,24 @@
 use phpDocumentor\Reflection\Fqsen;
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Object_;
+use phpDocumentor\Reflection\Types\String_;
 use PHPUnit\Framework\TestCase;
 
 class ClassStringTest extends TestCase
 {
+    public function testCreate(): void
+    {
+        $genericType = new Object_(new Fqsen('\Foo\Bar'));
+        $type = new ClassString($genericType);
+
+        $this->assertSame($genericType, $type->getGenericType());
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideClassStrings
+     * @dataProvider provideToStringData
      */
-    public function testClassStringStringifyCorrectly(ClassString $type, string $expectedString): void
+    public function testToString(ClassString $type, string $expectedString): void
     {
         $this->assertSame($expectedString, (string) $type);
     }
@@ -31,7 +41,7 @@ public function testClassStringStringifyCorrectly(ClassString $type, string $exp
     /**
      * @return array<string, array{ClassString, string}>
      */
-    public function provideClassStrings(): array
+    public function provideToStringData(): array
     {
         return [
             'generic class string' => [new ClassString(), 'class-string'],
diff --git a/tests/unit/PseudoTypes/ConditionalForParameterTest.php b/tests/unit/PseudoTypes/ConditionalForParameterTest.php
index bedae07..5a82240 100644
--- a/tests/unit/PseudoTypes/ConditionalForParameterTest.php
+++ b/tests/unit/PseudoTypes/ConditionalForParameterTest.php
@@ -6,6 +6,7 @@
 
 use phpDocumentor\Reflection\Types\Array_;
 use phpDocumentor\Reflection\Types\Integer;
+use phpDocumentor\Reflection\Types\Mixed_;
 use phpDocumentor\Reflection\Types\Static_;
 use PHPUnit\Framework\TestCase;
 
@@ -24,6 +25,7 @@ public function testCreate(): void
         $this->assertSame($targetType, $type->getTargetType());
         $this->assertSame($if, $type->getIf());
         $this->assertSame($else, $type->getElse());
+        $this->assertEquals(new Mixed_(), $type->underlyingType());
     }
 
     /**
diff --git a/tests/unit/PseudoTypes/ConditionalTest.php b/tests/unit/PseudoTypes/ConditionalTest.php
index 3e6f585..0093868 100644
--- a/tests/unit/PseudoTypes/ConditionalTest.php
+++ b/tests/unit/PseudoTypes/ConditionalTest.php
@@ -7,6 +7,7 @@
 use phpDocumentor\Reflection\Fqsen;
 use phpDocumentor\Reflection\Types\Array_;
 use phpDocumentor\Reflection\Types\Integer;
+use phpDocumentor\Reflection\Types\Mixed_;
 use phpDocumentor\Reflection\Types\Object_;
 use phpDocumentor\Reflection\Types\Static_;
 use PHPUnit\Framework\TestCase;
@@ -26,6 +27,7 @@ public function testCreate(): void
         $this->assertSame($targetType, $type->getTargetType());
         $this->assertSame($if, $type->getIf());
         $this->assertSame($else, $type->getElse());
+        $this->assertEquals(new Mixed_(), $type->underlyingType());
     }
 
     /**
diff --git a/tests/unit/PseudoTypes/ConstExpressionTest.php b/tests/unit/PseudoTypes/ConstExpressionTest.php
new file mode 100644
index 0000000..b26ca28
--- /dev/null
+++ b/tests/unit/PseudoTypes/ConstExpressionTest.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types\Mixed_;
+use phpDocumentor\Reflection\Types\Object_;
+use PHPUnit\Framework\TestCase;
+
+class ConstExpressionTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $owner = new Object_(new Fqsen('\Foo\Bar'));
+        $expression = '*';
+        $type = new ConstExpression($owner, $expression);
+
+        $this->assertSame($owner, $type->getOwner());
+        $this->assertSame($expression, $type->getExpression());
+        $this->assertEquals(new Mixed_(), $type->underlyingType());
+    }
+}
diff --git a/tests/unit/PseudoTypes/EnumStringTest.php b/tests/unit/PseudoTypes/EnumStringTest.php
new file mode 100644
index 0000000..9645e5d
--- /dev/null
+++ b/tests/unit/PseudoTypes/EnumStringTest.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types\Compound;
+use phpDocumentor\Reflection\Types\Object_;
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class EnumStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $genericType = new Object_(new Fqsen('\Foo\Bar'));
+        $type = new EnumString($genericType);
+
+        $this->assertSame($genericType, $type->getGenericType());
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    /**
+     * @dataProvider provideToStringData
+     */
+    public function testToString(EnumString $type, string $expectedString): void
+    {
+        $this->assertSame($expectedString, (string) $type);
+    }
+
+    /**
+     * @return array<string, array{EnumString, string}>
+     */
+    public function provideToStringData(): array
+    {
+        return [
+            'basic' => [new EnumString(), 'enum-string'],
+            'with generics' => [
+                new EnumString(new Object_(new Fqsen('\Foo\Bar'))),
+                'enum-string<\Foo\Bar>',
+            ],
+            'more than one enum' => [
+                new EnumString(
+                    new Compound([
+                        new Object_(new Fqsen('\Foo\Bar')),
+                        new Object_(new Fqsen('\Foo\Barrr')),
+                    ])
+                ),
+                'enum-string<\Foo\Bar|\Foo\Barrr>',
+            ],
+        ];
+    }
+}
diff --git a/tests/unit/PseudoTypes/FloatValueTest.php b/tests/unit/PseudoTypes/FloatValueTest.php
new file mode 100644
index 0000000..1d5db38
--- /dev/null
+++ b/tests/unit/PseudoTypes/FloatValueTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\Float_;
+use PHPUnit\Framework\TestCase;
+
+class FloatValueTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $value = 12.12;
+        $type = new FloatValue($value);
+
+        $this->assertSame($value, $type->getValue());
+        $this->assertEquals(new Float_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('12.12', (string) (new FloatValue(12.12)));
+    }
+}
diff --git a/tests/unit/PseudoTypes/HtmlEscapedStringTest.php b/tests/unit/PseudoTypes/HtmlEscapedStringTest.php
new file mode 100644
index 0000000..eeb635a
--- /dev/null
+++ b/tests/unit/PseudoTypes/HtmlEscapedStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class HtmlEscapedStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new HtmlEscapedString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('html-escaped-string', (string) (new HtmlEscapedString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/IntMaskOfTest.php b/tests/unit/PseudoTypes/IntMaskOfTest.php
index b48edfc..68eaa01 100644
--- a/tests/unit/PseudoTypes/IntMaskOfTest.php
+++ b/tests/unit/PseudoTypes/IntMaskOfTest.php
@@ -5,6 +5,7 @@
 namespace phpDocumentor\Reflection\PseudoTypes;
 
 use phpDocumentor\Reflection\Types\Compound;
+use phpDocumentor\Reflection\Types\Integer;
 use PHPUnit\Framework\TestCase;
 
 class IntMaskOfTest extends TestCase
@@ -15,6 +16,7 @@ public function testCreate(): void
         $type = new IntMaskOf($childType);
 
         $this->assertSame($childType, $type->getType());
+        $this->assertEquals(new Integer(), $type->underlyingType());
     }
 
     public function testToString(): void
diff --git a/tests/unit/PseudoTypes/IntMaskTest.php b/tests/unit/PseudoTypes/IntMaskTest.php
index e2e0881..cdeaee8 100644
--- a/tests/unit/PseudoTypes/IntMaskTest.php
+++ b/tests/unit/PseudoTypes/IntMaskTest.php
@@ -4,6 +4,7 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Integer;
 use PHPUnit\Framework\TestCase;
 
 class IntMaskTest extends TestCase
@@ -14,6 +15,7 @@ public function testCreate(): void
         $type = new IntMask(...$childTypes);
 
         $this->assertSame($childTypes, $type->getTypes());
+        $this->assertEquals(new Integer(), $type->underlyingType());
     }
 
     public function testToString(): void
diff --git a/tests/unit/PseudoTypes/IntRangeTest.php b/tests/unit/PseudoTypes/IntegerRangeTest.php
similarity index 53%
rename from tests/unit/PseudoTypes/IntRangeTest.php
rename to tests/unit/PseudoTypes/IntegerRangeTest.php
index cf32440..09bf27f 100644
--- a/tests/unit/PseudoTypes/IntRangeTest.php
+++ b/tests/unit/PseudoTypes/IntegerRangeTest.php
@@ -13,22 +13,34 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Integer;
 use PHPUnit\Framework\TestCase;
 
-class IntRangeTest extends TestCase
+class IntegerRangeTest extends TestCase
 {
+    public function testCreate(): void
+    {
+        $minValue = '-5';
+        $maxValue = '5';
+        $type = new IntegerRange($minValue, $maxValue);
+
+        $this->assertSame($minValue, $type->getMinValue());
+        $this->assertSame($maxValue, $type->getMaxValue());
+        $this->assertEquals(new Integer(), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideArrays
+     * @dataProvider provideToStringData
      */
-    public function testArrayStringifyCorrectly(IntegerRange $array, string $expectedString): void
+    public function testToString(IntegerRange $type, string $expectedString): void
     {
-        $this->assertSame($expectedString, (string) $array);
+        $this->assertSame($expectedString, (string) $type);
     }
 
     /**
-     * @return mixed[]
+     * @return array<string, array{IntegerRange, string}>
      */
-    public function provideArrays(): array
+    public function provideToStringData(): array
     {
         return [
             'simple int range' => [new IntegerRange('-5', '5'), 'int<-5, 5>'],
diff --git a/tests/unit/PseudoTypes/IntegerValueTest.php b/tests/unit/PseudoTypes/IntegerValueTest.php
new file mode 100644
index 0000000..fcc441f
--- /dev/null
+++ b/tests/unit/PseudoTypes/IntegerValueTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\Integer;
+use PHPUnit\Framework\TestCase;
+
+class IntegerValueTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $value = 12;
+        $type = new IntegerValue($value);
+
+        $this->assertSame($value, $type->getValue());
+        $this->assertEquals(new Integer(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('12', (string) (new IntegerValue(12)));
+    }
+}
diff --git a/tests/unit/PseudoTypes/InterfaceStringTest.php b/tests/unit/PseudoTypes/InterfaceStringTest.php
index 5a6becc..a56823e 100644
--- a/tests/unit/PseudoTypes/InterfaceStringTest.php
+++ b/tests/unit/PseudoTypes/InterfaceStringTest.php
@@ -16,14 +16,24 @@
 use phpDocumentor\Reflection\Fqsen;
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Object_;
+use phpDocumentor\Reflection\Types\String_;
 use PHPUnit\Framework\TestCase;
 
 class InterfaceStringTest extends TestCase
 {
+    public function testCreate(): void
+    {
+        $genericType = new Object_(new Fqsen('\Foo\Bar'));
+        $type = new InterfaceString($genericType);
+
+        $this->assertSame($genericType, $type->getGenericType());
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideInterfaceStrings
+     * @dataProvider provideToStringData
      */
-    public function testInterfaceStringStringifyCorrectly(InterfaceString $type, string $expectedString): void
+    public function testToString(InterfaceString $type, string $expectedString): void
     {
         $this->assertSame($expectedString, (string) $type);
     }
@@ -31,7 +41,7 @@ public function testInterfaceStringStringifyCorrectly(InterfaceString $type, str
     /**
      * @return array<string, array{InterfaceString, string}>
      */
-    public function provideInterfaceStrings(): array
+    public function provideToStringData(): array
     {
         return [
             'generic interface string' => [new InterfaceString(), 'interface-string'],
diff --git a/tests/unit/PseudoTypes/KeyOfTest.php b/tests/unit/PseudoTypes/KeyOfTest.php
index c96d837..001d0ab 100644
--- a/tests/unit/PseudoTypes/KeyOfTest.php
+++ b/tests/unit/PseudoTypes/KeyOfTest.php
@@ -16,6 +16,7 @@ public function testCreate(): void
         $type = new KeyOf($childType);
 
         $this->assertSame($childType, $type->getType());
+        $this->assertEquals(new ArrayKey(), $type->underlyingType());
     }
 
     public function testToString(): void
diff --git a/tests/unit/PseudoTypes/ListShapeTest.php b/tests/unit/PseudoTypes/ListShapeTest.php
new file mode 100644
index 0000000..034acd6
--- /dev/null
+++ b/tests/unit/PseudoTypes/ListShapeTest.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use PHPUnit\Framework\TestCase;
+
+class ListShapeTest extends TestCase
+{
+    public function testToString(): void
+    {
+        $type = new ListShape(new ListShapeItem(null, new IntegerValue(1), false));
+
+        $this->assertSame('list{1}', (string) $type);
+    }
+}
diff --git a/tests/unit/PseudoTypes/ListTest.php b/tests/unit/PseudoTypes/ListTest.php
index 6fb313e..8f51c51 100644
--- a/tests/unit/PseudoTypes/ListTest.php
+++ b/tests/unit/PseudoTypes/ListTest.php
@@ -13,6 +13,7 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Array_;
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Integer;
 use phpDocumentor\Reflection\Types\Mixed_;
@@ -21,18 +22,29 @@
 
 class ListTest extends TestCase
 {
+    public function testCreateWithoutParams(): void
+    {
+        $type = new List_();
+
+        $this->assertEquals(new Integer(), $type->getOriginalKeyType());
+        $this->assertNull($type->getOriginalValueType());
+        $this->assertEquals(new Integer(), $type->getKeyType());
+        $this->assertEquals(new Mixed_(), $type->getValueType());
+        $this->assertEquals(new Array_(), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideArrays
+     * @dataProvider provideToStringData
      */
-    public function testArrayStringifyCorrectly(List_ $array, string $expectedString): void
+    public function testToString(List_ $array, string $expectedString): void
     {
         $this->assertSame($expectedString, (string) $array);
     }
 
     /**
-     * @return mixed[]
+     * @return array<string, array{List_, string}>
      */
-    public function provideArrays(): array
+    public function provideToStringData(): array
     {
         return [
             'simple list' => [new List_(), 'list'],
diff --git a/tests/unit/PseudoTypes/LiteralStringTest.php b/tests/unit/PseudoTypes/LiteralStringTest.php
new file mode 100644
index 0000000..ef5131f
--- /dev/null
+++ b/tests/unit/PseudoTypes/LiteralStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class LiteralStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new LiteralString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('literal-string', (string) (new LiteralString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/LowercaseStringTest.php b/tests/unit/PseudoTypes/LowercaseStringTest.php
new file mode 100644
index 0000000..8f358fd
--- /dev/null
+++ b/tests/unit/PseudoTypes/LowercaseStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class LowercaseStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new LowercaseString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('lowercase-string', (string) (new LowercaseString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/NegativeIntegerTest.php b/tests/unit/PseudoTypes/NegativeIntegerTest.php
new file mode 100644
index 0000000..8c889d3
--- /dev/null
+++ b/tests/unit/PseudoTypes/NegativeIntegerTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\Integer;
+use PHPUnit\Framework\TestCase;
+
+class NegativeIntegerTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new NegativeInteger();
+
+        $this->assertEquals(new Integer(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('negative-int', (string) (new NegativeInteger()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/NonEmptyArrayTest.php b/tests/unit/PseudoTypes/NonEmptyArrayTest.php
index 0ae5acd..0531179 100644
--- a/tests/unit/PseudoTypes/NonEmptyArrayTest.php
+++ b/tests/unit/PseudoTypes/NonEmptyArrayTest.php
@@ -13,6 +13,7 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Array_;
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Integer;
 use phpDocumentor\Reflection\Types\Mixed_;
@@ -21,18 +22,29 @@
 
 class NonEmptyArrayTest extends TestCase
 {
+    public function testCreateWithoutParams(): void
+    {
+        $type = new NonEmptyArray();
+
+        $this->assertNull($type->getOriginalKeyType());
+        $this->assertNull($type->getOriginalValueType());
+        $this->assertEquals(new Compound([new String_(), new Integer()]), $type->getKeyType());
+        $this->assertEquals(new Mixed_(), $type->getValueType());
+        $this->assertEquals(new Array_(), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideArrays
+     * @dataProvider provideToStringData
      */
-    public function testArrayStringifyCorrectly(NonEmptyArray $array, string $expectedString): void
+    public function testToString(NonEmptyArray $type, string $expectedString): void
     {
-        $this->assertSame($expectedString, (string) $array);
+        $this->assertSame($expectedString, (string) $type);
     }
 
     /**
-     * @return mixed[]
+     * @return array<string, array{NonEmptyArray, string}>
      */
-    public function provideArrays(): array
+    public function provideToStringData(): array
     {
         return [
             'simple non-empty-array' => [new NonEmptyArray(), 'non-empty-array'],
diff --git a/tests/unit/PseudoTypes/NonEmptyListTest.php b/tests/unit/PseudoTypes/NonEmptyListTest.php
index 69dedd7..75cd2f6 100644
--- a/tests/unit/PseudoTypes/NonEmptyListTest.php
+++ b/tests/unit/PseudoTypes/NonEmptyListTest.php
@@ -13,6 +13,7 @@
 
 namespace phpDocumentor\Reflection\PseudoTypes;
 
+use phpDocumentor\Reflection\Types\Array_;
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Integer;
 use phpDocumentor\Reflection\Types\Mixed_;
@@ -21,18 +22,29 @@
 
 class NonEmptyListTest extends TestCase
 {
+    public function testCreateWithoutParams(): void
+    {
+        $type = new NonEmptyList();
+
+        $this->assertEquals(new Integer(), $type->getOriginalKeyType());
+        $this->assertNull($type->getOriginalValueType());
+        $this->assertEquals(new Integer(), $type->getKeyType());
+        $this->assertEquals(new Mixed_(), $type->getValueType());
+        $this->assertEquals(new Array_(null, new Integer()), $type->underlyingType());
+    }
+
     /**
-     * @dataProvider provideArrays
+     * @dataProvider provideToStringData
      */
-    public function testArrayStringifyCorrectly(NonEmptyList $array, string $expectedString): void
+    public function testToString(NonEmptyList $array, string $expectedString): void
     {
         $this->assertSame($expectedString, (string) $array);
     }
 
     /**
-     * @return mixed[]
+     * @return array<string, array{NonEmptyList, string}>
      */
-    public function provideArrays(): array
+    public function provideToStringData(): array
     {
         return [
             'simple non-empty-list' => [new NonEmptyList(), 'non-empty-list'],
diff --git a/tests/unit/PseudoTypes/NonEmptyLowercaseStringTest.php b/tests/unit/PseudoTypes/NonEmptyLowercaseStringTest.php
new file mode 100644
index 0000000..291f856
--- /dev/null
+++ b/tests/unit/PseudoTypes/NonEmptyLowercaseStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class NonEmptyLowercaseStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new NonEmptyLowercaseString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('non-empty-lowercase-string', (string) (new NonEmptyLowercaseString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/NonEmptyStringTest.php b/tests/unit/PseudoTypes/NonEmptyStringTest.php
new file mode 100644
index 0000000..9dc9226
--- /dev/null
+++ b/tests/unit/PseudoTypes/NonEmptyStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class NonEmptyStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new NonEmptyString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('non-empty-string', (string) (new NonEmptyString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/NumericStringTest.php b/tests/unit/PseudoTypes/NumericStringTest.php
new file mode 100644
index 0000000..c3b9a8b
--- /dev/null
+++ b/tests/unit/PseudoTypes/NumericStringTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class NumericStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new NumericString();
+
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('numeric-string', (string) (new NumericString()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/ObjectShapeTest.php b/tests/unit/PseudoTypes/ObjectShapeTest.php
new file mode 100644
index 0000000..b5c6268
--- /dev/null
+++ b/tests/unit/PseudoTypes/ObjectShapeTest.php
@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\Object_;
+use PHPUnit\Framework\TestCase;
+
+class ObjectShapeTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $item1 = new ObjectShapeItem('foo', new True_(), false);
+        $item2 = new ObjectShapeItem('bar', new False_(), true);
+
+        $objectShape = new ObjectShape($item1, $item2);
+
+        $this->assertSame([$item1, $item2], $objectShape->getItems());
+        $this->assertEquals(new Object_(), $objectShape->underlyingType());
+    }
+
+    /**
+     * @dataProvider provideToStringData
+     */
+    public function testToString(string $expectedResult, ObjectShape $objectShape): void
+    {
+        $this->assertSame($expectedResult, (string) $objectShape);
+    }
+
+    /**
+     * @return array<string, array{string, ObjectShape}>
+     */
+    public static function provideToStringData(): array
+    {
+        return [
+            'with keys' => [
+                'object{foo: true, bar?: false}',
+                new ObjectShape(
+                    new ObjectShapeItem('foo', new True_(), false),
+                    new ObjectShapeItem('bar', new False_(), true)
+                ),
+            ],
+            'with empty keys' => [
+                'object{true, false}',
+                new ObjectShape(
+                    new ObjectShapeItem('', new True_(), false),
+                    new ObjectShapeItem('', new False_(), false)
+                ),
+            ],
+            'without keys' => [
+                'object{true, false}',
+                new ObjectShape(
+                    new ObjectShapeItem(null, new True_(), false),
+                    new ObjectShapeItem(null, new False_(), false)
+                ),
+            ],
+        ];
+    }
+}
diff --git a/tests/unit/PseudoTypes/OffsetAccessTest.php b/tests/unit/PseudoTypes/OffsetAccessTest.php
index 44afa04..ccb354f 100644
--- a/tests/unit/PseudoTypes/OffsetAccessTest.php
+++ b/tests/unit/PseudoTypes/OffsetAccessTest.php
@@ -5,6 +5,7 @@
 namespace phpDocumentor\Reflection\PseudoTypes;
 
 use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types\Mixed_;
 use phpDocumentor\Reflection\Types\Object_;
 use PHPUnit\Framework\TestCase;
 
@@ -18,6 +19,7 @@ public function testCreate(): void
 
         $this->assertSame($mainType, $type->getType());
         $this->assertSame($offset, $type->getOffset());
+        $this->assertEquals(new Mixed_(), $type->underlyingType());
     }
 
     /**
diff --git a/tests/unit/PseudoTypes/PositiveIntegerTest.php b/tests/unit/PseudoTypes/PositiveIntegerTest.php
new file mode 100644
index 0000000..385e02a
--- /dev/null
+++ b/tests/unit/PseudoTypes/PositiveIntegerTest.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\Integer;
+use PHPUnit\Framework\TestCase;
+
+class PositiveIntegerTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $type = new PositiveInteger();
+
+        $this->assertEquals(new Integer(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('positive-int', (string) (new PositiveInteger()));
+    }
+}
diff --git a/tests/unit/PseudoTypes/StringValueTest.php b/tests/unit/PseudoTypes/StringValueTest.php
new file mode 100644
index 0000000..5c582de
--- /dev/null
+++ b/tests/unit/PseudoTypes/StringValueTest.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class StringValueTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $value = 'abcdef';
+        $type = new StringValue($value);
+
+        $this->assertSame($value, $type->getValue());
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    public function testToString(): void
+    {
+        $this->assertSame('"abcd"', (string) (new StringValue('abcd')));
+    }
+}
diff --git a/tests/unit/PseudoTypes/TraitStringTest.php b/tests/unit/PseudoTypes/TraitStringTest.php
new file mode 100644
index 0000000..22ca0c1
--- /dev/null
+++ b/tests/unit/PseudoTypes/TraitStringTest.php
@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\PseudoTypes;
+
+use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types\Compound;
+use phpDocumentor\Reflection\Types\Object_;
+use phpDocumentor\Reflection\Types\String_;
+use PHPUnit\Framework\TestCase;
+
+class TraitStringTest extends TestCase
+{
+    public function testCreate(): void
+    {
+        $genericType = new Object_(new Fqsen('\Foo\Bar'));
+        $type = new TraitString($genericType);
+
+        $this->assertSame($genericType, $type->getGenericType());
+        $this->assertEquals(new String_(), $type->underlyingType());
+    }
+
+    /**
+     * @dataProvider provideToStringData
+     */
+    public function testToString(TraitString $type, string $expectedString): void
+    {
+        $this->assertSame($expectedString, (string) $type);
+    }
+
+    /**
+     * @return array<string, array{TraitString, string}>
+     */
+    public function provideToStringData(): array
+    {
+        return [
+            'basic' => [new TraitString(), 'trait-string'],
+            'with generic' => [
+                new TraitString(new Object_(new Fqsen('\Foo\Bar'))),
+                'trait-string<\Foo\Bar>',
+            ],
+            'with compound generic' => [
+                new TraitString(
+                    new Compound([
+                        new Object_(new Fqsen('\Foo\Bar')),
+                        new Object_(new Fqsen('\Foo\Barrr')),
+                    ])
+                ),
+                'trait-string<\Foo\Bar|\Foo\Barrr>',
+            ],
+        ];
+    }
+}
diff --git a/tests/unit/PseudoTypes/ValueOfTest.php b/tests/unit/PseudoTypes/ValueOfTest.php
index 2fc6f87..9a1b7d1 100644
--- a/tests/unit/PseudoTypes/ValueOfTest.php
+++ b/tests/unit/PseudoTypes/ValueOfTest.php
@@ -5,6 +5,7 @@
 namespace phpDocumentor\Reflection\PseudoTypes;
 
 use phpDocumentor\Reflection\Fqsen;
+use phpDocumentor\Reflection\Types\Mixed_;
 use phpDocumentor\Reflection\Types\Object_;
 use PHPUnit\Framework\TestCase;
 
@@ -16,6 +17,7 @@ public function testCreate(): void
         $type = new ValueOf($childType);
 
         $this->assertSame($childType, $type->getType());
+        $this->assertEquals(new Mixed_(), $type->underlyingType());
     }
 
     public function testToString(): void
diff --git a/tests/unit/TypeResolverTest.php b/tests/unit/TypeResolverTest.php
index fadc9fe..7d6bfe8 100644
--- a/tests/unit/TypeResolverTest.php
+++ b/tests/unit/TypeResolverTest.php
@@ -880,6 +880,10 @@ public function typeProvider(): array
                     new StringValue('bar')
                 ),
             ],
+            [
+                '100.5',
+                new FloatValue(100.5),
+            ],
         ];
     }