test: add comprehensive tests for TemplateVariables

Add 21 tests with 53 assertions covering:
- Setters/getters for all 9 variables (via DataProvider)
- Null returns for unset variables
- Array conversion and merge functionality
- Whitelist validation (rejects unknown variables)
- Type validation (rejects wrong types)
- Invalid method calls

Use PHP 8 attributes for DataProviders for cleaner syntax.

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

tests/php/Unit/Handler/TemplateVariablesTest.php

@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2025 LibreCode coop and contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Libresign\Tests\Unit\Handler;
+
+use OCA\Libresign\Handler\TemplateVariables;
+use OCA\Libresign\Tests\Unit\TestCase;
+use PHPUnit\Framework\Attributes\DataProvider;
+
+/**
+ * @internal
+ */
+final class TemplateVariablesTest extends TestCase {
+	private TemplateVariables $variables;
+
+	public function setUp(): void {
+		parent::setUp();
+		$this->variables = new TemplateVariables();
+	}
+
+	public static function provideValidValues(): array {
+		return [
+			'uuid' => ['uuid', 'test-uuid-123'],
+			'signers' => ['signers', [['name' => 'John']]],
+			'signedBy' => ['signedBy', 'LibreSign'],
+			'direction' => ['direction', 'ltr'],
+			'linkToSite' => ['linkToSite', 'https://example.com'],
+			'validationSite' => ['validationSite', 'https://validate.com'],
+			'validateIn' => ['validateIn', 'Validate in %s'],
+			'qrcode' => ['qrcode', 'base64string'],
+			'qrcodeSize' => ['qrcodeSize', 108],
+		];
+	}
+
+	#[DataProvider('provideValidValues')]
+	public function testSettersAndGetters(string $variable, mixed $value): void {
+		$setter = 'set' . ucfirst($variable);
+		$getter = 'get' . ucfirst($variable);
+
+		$result = $this->variables->$setter($value);
+		$this->assertSame($this->variables, $result);
+
+		$this->assertSame($value, $this->variables->$getter());
+
+		$this->assertTrue($this->variables->has($variable));
+	}
+
+	public function testGettersReturnNullForUnsetVariables(): void {
+		$this->assertNull($this->variables->getUuid());
+		$this->assertNull($this->variables->getQrcodeSize());
+	}
+
+	public function testToArrayAndMerge(): void {
+		$this->variables->setUuid('uuid-123')->setSignedBy('Signer');
+
+		$array = $this->variables->toArray();
+		$this->assertSame(['uuid' => 'uuid-123', 'signedBy' => 'Signer'], $array);
+
+		$result = $this->variables->merge(['uuid' => 'new-uuid', 'direction' => 'rtl']);
+		$this->assertSame($this->variables, $result);
+		$this->assertSame('new-uuid', $this->variables->getUuid());
+		$this->assertSame('rtl', $this->variables->getDirection());
+	}
+
+	public static function provideInvalidVariables(): array {
+		return [
+			['setInvalidVar'],
+			['getInvalidVar'],
+		];
+	}
+
+	#[DataProvider('provideInvalidVariables')]
+	public function testRejectsInvalidVariables(string $method): void {
+		$this->expectException(\InvalidArgumentException::class);
+		$this->expectExceptionMessage("Template variable 'invalidVar' is not allowed");
+
+		$this->variables->$method('value');
+	}
+
+	public function testMergeRejectsInvalidVariables(): void {
+		$this->expectException(\InvalidArgumentException::class);
+		$this->expectExceptionMessage("Template variable 'invalidVar' is not allowed");
+
+		$this->variables->merge(['invalidVar' => 'value']);
+	}
+
+	public static function provideInvalidTypes(): array {
+		return [
+			'uuid expects string' => ['uuid', 123, 'string', 'integer'],
+			'signers expects array' => ['signers', 'string', 'array', 'string'],
+			'qrcodeSize expects integer' => ['qrcodeSize', '108', 'integer', 'string'],
+		];
+	}
+
+	#[DataProvider('provideInvalidTypes')]
+	public function testRejectsInvalidTypes(string $variable, mixed $value, string $expected, string $actual): void {
+		$this->expectException(\InvalidArgumentException::class);
+		$this->expectExceptionMessage("must be of type {$expected}, got {$actual}");
+
+		$method = 'set' . ucfirst($variable);
+		$this->variables->$method($value);
+	}
+
+	#[DataProvider('provideInvalidTypes')]
+	public function testMergeRejectsInvalidTypes(string $variable, mixed $value, string $expected, string $actual): void {
+		$this->expectException(\InvalidArgumentException::class);
+		$this->expectExceptionMessage("must be of type {$expected}, got {$actual}");
+
+		$this->variables->merge([$variable => $value]);
+	}
+
+	public function testRejectsInvalidMethod(): void {
+		$this->expectException(\BadMethodCallException::class);
+		$this->expectExceptionMessage("Method invalidMethod does not exist");
+
+		$this->variables->invalidMethod();
+	}
+}