Enhancement: Implement integer increment and decrement mutators

.travis.yml

@@ -24,7 +24,7 @@ matrix:
 
 env:
   global:
-    - INFECTION_FLAGS='--threads=4 --min-msi=59 --min-covered-msi=86'
+    - INFECTION_FLAGS='--threads=4 --min-msi=57 --min-covered-msi=84'
 
 cache:
   directories:

src/Config/InfectionConfig.php

@@ -50,6 +50,8 @@
 use Infection\Mutator\ConditionalNegotiation\NotIdentical;
 use Infection\Mutator\FunctionSignature\ProtectedVisibility;
 use Infection\Mutator\FunctionSignature\PublicVisibility;
+use Infection\Mutator\Number\DecrementInteger;
+use Infection\Mutator\Number\IncrementInteger;
 use Infection\Mutator\Number\OneZeroFloat;
 use Infection\Mutator\Number\OneZeroInteger;
 use Infection\Mutator\Operator\Break_;
@@ -118,6 +120,8 @@ class InfectionConfig
         NotIdentical::class,
 
         // Number
+        DecrementInteger::class,
+        IncrementInteger::class,
         OneZeroInteger::class,
         OneZeroFloat::class,
 

src/Mutator/Number/DecrementInteger.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * Copyright © 2017-2018 Maks Rafalko
+ *
+ * License: https://opensource.org/licenses/BSD-3-Clause New BSD License
+ */
+declare(strict_types=1);
+
+namespace Infection\Mutator\Number;
+
+use Infection\Mutator\Mutator;
+use PhpParser\Node;
+
+class DecrementInteger extends Mutator
+{
+    /**
+     * Decrements an integer by 1.
+     *
+     * @param Node $node
+     *
+     * @return Node\Scalar\LNumber
+     */
+    public function mutate(Node $node)
+    {
+        return new Node\Scalar\LNumber($node->value - 1);
+    }
+
+    public function shouldMutate(Node $node): bool
+    {
+        return $node instanceof Node\Scalar\LNumber && $node->value !== 1;
+    }
+}

src/Mutator/Number/IncrementInteger.php

@@ -0,0 +1,32 @@
+<?php
+/**
+ * Copyright © 2017-2018 Maks Rafalko
+ *
+ * License: https://opensource.org/licenses/BSD-3-Clause New BSD License
+ */
+declare(strict_types=1);
+
+namespace Infection\Mutator\Number;
+
+use Infection\Mutator\Mutator;
+use PhpParser\Node;
+
+class IncrementInteger extends Mutator
+{
+    /**
+     * Increments an integer by 1.
+     *
+     * @param Node $node
+     *
+     * @return Node\Scalar\LNumber
+     */
+    public function mutate(Node $node)
+    {
+        return new Node\Scalar\LNumber($node->value + 1);
+    }
+
+    public function shouldMutate(Node $node): bool
+    {
+        return $node instanceof Node\Scalar\LNumber && $node->value !== 0;
+    }
+}

tests/Mutator/Number/DecrementIntegerTest.php

@@ -0,0 +1,73 @@
+<?php
+/**
+ * Copyright © 2017-2018 Maks Rafalko
+ *
+ * License: https://opensource.org/licenses/BSD-3-Clause New BSD License
+ */
+declare(strict_types=1);
+
+namespace Infection\Tests\Mutator\Number;
+
+use Infection\Mutator\Mutator;
+use Infection\Mutator\Number\DecrementInteger;
+use Infection\Mutator\Number\OneZeroInteger;
+use Infection\Tests\Mutator\AbstractMutator;
+
+class DecrementIntegerTest extends AbstractMutator
+{
+    public function test_it_decrements_an_integer()
+    {
+        $code = <<<'PHP'
+<?php
+
+if ($foo < 10) {
+    echo 'bar';
+}
+PHP;
+
+        $mutatedCode = $this->mutate($code);
+
+        $expectedMutatedCode = <<<'PHP'
+<?php
+
+if ($foo < 9) {
+    echo 'bar';
+}
+PHP;
+
+        $this->assertSame($expectedMutatedCode, $mutatedCode);
+    }
+
+    /**
+     * Mutator should skip 1 to reduce the number of mutations.
+     *
+     * @see OneZeroInteger::mutate()
+     */
+    public function test_it_does_not_decrement_one()
+    {
+        $code = <<<'PHP'
+<?php
+
+if ($foo < 1) {
+    echo 'bar';
+}
+PHP;
+
+        $mutatedCode = $this->mutate($code);
+
+        $expectedMutatedCode = <<<'PHP'
+<?php
+
+if ($foo < 1) {
+    echo 'bar';
+}
+PHP;
+
+        $this->assertSame($expectedMutatedCode, $mutatedCode);
+    }
+
+    protected function getMutator(): Mutator
+    {
+        return new DecrementInteger();
+    }
+}

tests/Mutator/Number/IncrementIntegerTest.php

@@ -0,0 +1,73 @@
+<?php
+/**
+ * Copyright © 2017-2018 Maks Rafalko
+ *
+ * License: https://opensource.org/licenses/BSD-3-Clause New BSD License
+ */
+declare(strict_types=1);
+
+namespace Infection\Tests\Mutator\Number;
+
+use Infection\Mutator\Mutator;
+use Infection\Mutator\Number\IncrementInteger;
+use Infection\Mutator\Number\OneZeroInteger;
+use Infection\Tests\Mutator\AbstractMutator;
+
+class IncrementIntegerTest extends AbstractMutator
+{
+    public function test_it_increments_an_integer()
+    {
+        $code = <<<'PHP'
+<?php
+
+if ($foo < 10) {
+    echo 'bar';
+}
+PHP;
+
+        $mutatedCode = $this->mutate($code);
+
+        $expectedMutatedCode = <<<'PHP'
+<?php
+
+if ($foo < 11) {
+    echo 'bar';
+}
+PHP;
+
+        $this->assertSame($expectedMutatedCode, $mutatedCode);
+    }
+
+    /**
+     * Mutator should skip 0 to reduce the number of mutations.
+     *
+     * @see OneZeroInteger::mutate()
+     */
+    public function test_it_does_not_increment_zero()
+    {
+        $code = <<<'PHP'
+<?php
+
+if ($foo < 0) {
+    echo 'bar';
+}
+PHP;
+
+        $mutatedCode = $this->mutate($code);
+
+        $expectedMutatedCode = <<<'PHP'
+<?php
+
+if ($foo < 0) {
+    echo 'bar';
+}
+PHP;
+
+        $this->assertSame($expectedMutatedCode, $mutatedCode);
+    }
+
+    protected function getMutator(): Mutator
+    {
+        return new IncrementInteger();
+    }
+}