diff --git a/src/Types/ArraySchema.php b/src/Types/ArraySchema.php
index 54de85e..2c4cc58 100644
--- a/src/Types/ArraySchema.php
+++ b/src/Types/ArraySchema.php
@@ -43,7 +43,7 @@ public function contains(Schema $schema): static
     public function minContains(int $min): static
     {
         if ($min < 0) {
-            throw new SchemaException('minContains must be non-negative');
+            throw new SchemaException('minContains must be greater than or equal to 0');
         }
 
         if ($this->maxContains !== null && $min > $this->maxContains) {
@@ -63,7 +63,7 @@ public function minContains(int $min): static
     public function maxContains(int $max): static
     {
         if ($max < 0) {
-            throw new SchemaException('maxContains must be non-negative');
+            throw new SchemaException('maxContains must be greater than or equal to 0');
         }
 
         if ($this->minContains !== null && $max < $this->minContains) {
diff --git a/tests/ArchitectureTest.php b/tests/ArchitectureTest.php
index c0fb154..0bcddd9 100644
--- a/tests/ArchitectureTest.php
+++ b/tests/ArchitectureTest.php
@@ -4,5 +4,11 @@
 
 namespace Cortex\JsonSchema\Tests;
 
+use Throwable;
+
 arch()->preset()->php();
 arch()->preset()->security();
+
+arch()->expect('Cortex\JsonSchema\Contracts')->toBeInterfaces();
+arch()->expect('Cortex\JsonSchema\Enums')->toBeEnums();
+arch()->expect('Cortex\JsonSchema\Exceptions')->toExtend(Throwable::class);
diff --git a/tests/Unit/SchemaFactoryTest.php b/tests/Unit/SchemaFactoryTest.php
index 727b215..ba49980 100644
--- a/tests/Unit/SchemaFactoryTest.php
+++ b/tests/Unit/SchemaFactoryTest.php
@@ -87,4 +87,6 @@
             'fooArray',
         ],
     ]);
+
+    expect($schema->toJson())->toBe(json_encode($schema->toArray()));
 });
diff --git a/tests/Unit/Targets/ArraySchemaTest.php b/tests/Unit/Targets/ArraySchemaTest.php
index 90476ce..1e470c7 100644
--- a/tests/Unit/Targets/ArraySchemaTest.php
+++ b/tests/Unit/Targets/ArraySchemaTest.php
@@ -123,3 +123,15 @@
         'At least one array item must match schema',
     );
 });
+
+it('throws an exception if the minContains is less than 0', function (): void {
+    Schema::array('numbers')
+        ->description('List of numbers')
+        ->minContains(-1);
+})->throws(SchemaException::class, 'minContains must be greater than or equal to 0');
+
+it('throws an exception if the maxContains is less than 0', function (): void {
+    Schema::array('numbers')
+        ->description('List of numbers')
+        ->maxContains(-1);
+})->throws(SchemaException::class, 'maxContains must be greater than or equal to 0');
diff --git a/tests/Unit/Targets/IntegerSchemaTest.php b/tests/Unit/Targets/IntegerSchemaTest.php
index 8893800..f6d308e 100644
--- a/tests/Unit/Targets/IntegerSchemaTest.php
+++ b/tests/Unit/Targets/IntegerSchemaTest.php
@@ -156,3 +156,9 @@
         'The data (string) must match the type: integer, null',
     );
 });
+
+it('throws an exception if the multipleOf is less than 0', function (): void {
+    Schema::integer('age')
+        ->description('User age')
+        ->multipleOf(-1);
+})->throws(SchemaException::class, 'multipleOf must be greater than 0');
diff --git a/tests/Unit/Targets/ObjectSchemaTest.php b/tests/Unit/Targets/ObjectSchemaTest.php
index e68882d..51f9451 100644
--- a/tests/Unit/Targets/ObjectSchemaTest.php
+++ b/tests/Unit/Targets/ObjectSchemaTest.php
@@ -173,3 +173,25 @@
         'key2' => 'value2',
     ]))->not->toThrow(SchemaException::class);
 });
+
+it('can specify a propertyNames schema', function (): void {
+    $schema = Schema::object('user')
+        ->properties(
+            Schema::string('name')->required(),
+        )
+        // ->additionalProperties(true)
+        ->propertyNames(Schema::string()->pattern('^[a-zA-Z]+$'));
+
+    $schemaArray = $schema->toArray();
+
+    expect($schemaArray)->toHaveKey('propertyNames.pattern', '^[a-zA-Z]+$');
+
+    // Validation tests
+    expect(fn() => $schema->validate([
+        'name' => 'John Doe',
+    ]))->not->toThrow(SchemaException::class);
+
+    expect(fn() => $schema->validate([
+        'name' => 123, // invalid property name pattern
+    ]))->toThrow(SchemaException::class, 'The properties must match schema: name');
+});
diff --git a/tests/Unit/Targets/StringSchemaTest.php b/tests/Unit/Targets/StringSchemaTest.php
index 5026a2b..273dfff 100644
--- a/tests/Unit/Targets/StringSchemaTest.php
+++ b/tests/Unit/Targets/StringSchemaTest.php
@@ -105,6 +105,12 @@
     );
 
     expect(fn() => $schema->validate('test@example.com'))->not->toThrow(SchemaException::class);
+
+    $schema = Schema::string('email')
+        ->description('User email address')
+        ->format('custom');
+
+    expect($schema->toArray())->toHaveKey('format', 'custom');
 });
 
 it('can create a nullable string schema', function (): void {
@@ -122,10 +128,14 @@
     expect(fn() => $schema->validate(null))->not->toThrow(SchemaException::class);
     expect(fn() => $schema->validate('John'))->not->toThrow(SchemaException::class);
 
+    expect($schema->isValid(null))->toBeTrue();
+    expect($schema->isValid('John'))->toBeTrue();
+
     expect(fn() => $schema->validate(123))->toThrow(
         SchemaException::class,
         'The data (integer) must match the type: string, null',
     );
+    expect($schema->isValid(123))->toBeFalse();
 });
 
 it('can create a read-only string schema', function (): void {