diff --git a/tests/Composer/Test/Command/BaseDependencyCommandTest.php b/tests/Composer/Test/Command/BaseDependencyCommandTest.php
new file mode 100644
index 000000000..78b41d223
--- /dev/null
+++ b/tests/Composer/Test/Command/BaseDependencyCommandTest.php
@@ -0,0 +1,457 @@
+<?php declare(strict_types=1);
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+
+namespace Composer\Test\Command;
+
+use Composer\Semver\Constraint\Constraint;
+use Composer\Semver\Constraint\MatchAllConstraint;
+use Symfony\Component\Console\Command\Command;
+use UnexpectedValueException;
+use InvalidArgumentException;
+use Composer\Test\TestCase;
+use Composer\Package\Link;
+use RuntimeException;
+use Generator;
+
+class BaseDependencyCommandTest extends TestCase
+{
+    /**
+     * Test that an exception is throw when there weren't provided some parameters
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider noParametersCaseProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testExceptionWhenNoRequiredParameters(
+        string $command,
+        array $parameters,
+        string $expectedExceptionMessage
+    ): void {
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage($expectedExceptionMessage);
+
+        $appTester = $this->getApplicationTester();
+        $this->assertEquals(Command::FAILURE, $appTester->run(['command' => $command] + $parameters));
+    }
+
+    /**
+     * @return Generator<string, array{string, array<string, string>, string}>
+     */
+    public static function noParametersCaseProvider(): Generator
+    {
+        yield '`why` command without package parameter' => [
+            'why',
+            [],
+            'Not enough arguments (missing: "package").'
+        ];
+
+        yield '`why-not` command without package and version parameters' => [
+            'why-not',
+            [],
+            'Not enough arguments (missing: "package, version").'
+        ];
+
+        yield '`why-not` command without package parameter' => [
+            'why-not',
+            ['version' => '*'],
+            'Not enough arguments (missing: "package").'
+        ];
+
+        yield '`why-not` command without version parameter' => [
+            'why-not',
+            ['package' => 'vendor1/package1'],
+            'Not enough arguments (missing: "version").'
+        ];
+    }
+
+    /**
+     * Test that an exception is throw when there wasn't provided the locked file alongside `--locked` parameter
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider caseProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testExceptionWhenRunningLockedWithoutLockFile(string $command, array $parameters): void
+    {
+        $this->initTempComposer();
+
+        $this->expectException(UnexpectedValueException::class);
+        $this->expectExceptionMessage('A valid composer.lock file is required to run this command with --locked');
+
+        $appTester = $this->getApplicationTester();
+        $this->assertEquals(
+            Command::FAILURE,
+            $appTester->run(['command' => $command] + $parameters + ['--locked' => true]
+            )
+        );
+    }
+
+    /**
+     * Test that an exception is throw when the provided package to be inspected isn't required by the project
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider caseProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testExceptionWhenItCouldNotFoundThePackage(string $command, array $parameters): void
+    {
+        $packageToBeInspected = $parameters['package'];
+
+        $this->initTempComposer();
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage(sprintf('Could not find package "%s" in your project', $packageToBeInspected));
+
+        $appTester = $this->getApplicationTester();
+        $this->assertEquals(
+            Command::FAILURE,
+            $appTester->run(['command' => $command] + $parameters)
+        );
+    }
+
+    /**
+     * Test that it shows a warning message when the package to be inspected wasn't found in the project
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider caseProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testExceptionWhenPackageWasNotFoundInProject(string $command, array $parameters): void
+    {
+        $packageToBeInspected = $parameters['package'];
+
+        $this->initTempComposer([
+            'require' => [
+                'vendor1/package2' => '1.*',
+                'vendor2/package1' => '2.*'
+            ]
+        ]);
+
+        $firstRequiredPackage = self::getPackage('vendor1/package2');
+        $secondRequiredPackage = self::getPackage('vendor2/package1');
+
+        $this->createInstalledJson([$firstRequiredPackage, $secondRequiredPackage]);
+        $this->createComposerLock([$firstRequiredPackage, $secondRequiredPackage]);
+
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage(sprintf('Could not find package "%s" in your project', $packageToBeInspected));
+
+        $appTester = $this->getApplicationTester();
+
+        $this->assertEquals(Command::FAILURE, $appTester->run(['command' => $command] + $parameters));
+    }
+
+    /**
+     * Test that it shows a warning message when the dependencies haven't been installed yet
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider caseProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testWarningWhenDependenciesAreNotInstalled(string $command, array $parameters): void
+    {
+        $expectedWarningMessage = '<warning>No dependencies installed. Try running composer install or update, or use --locked.</warning>';
+
+        $this->initTempComposer([
+            'require' => [
+                'vendor1/package1' => '1.*'
+            ],
+            'require-dev' => [
+                'vendor2/package1' => '2.*'
+            ]
+        ]);
+
+        $someRequiredPackage = self::getPackage('vendor1/package1');
+        $someDevRequiredPackage = self::getPackage('vendor2/package1');
+
+        $this->createComposerLock([$someRequiredPackage], [$someDevRequiredPackage]);
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => $command] + $parameters);
+
+        $this->assertSame($expectedWarningMessage, trim($appTester->getDisplay(true)));
+    }
+
+    /**
+     * @return Generator<string, array{string, array<string, string>}>
+     */
+    public static function caseProvider(): Generator
+    {
+        yield '`why` command' => [
+            'why',
+            ['package' => 'vendor1/package1']
+        ];
+
+        yield '`why-not` command' => [
+            'why-not',
+            ['package' => 'vendor1/package1', 'version' => '1.*']
+        ];
+    }
+
+    /**
+     * Test that it finishes successfully and show some expected outputs depending on different command parameters
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\DependsCommand
+     *
+     * @dataProvider caseWhyProvider
+     *
+     * @param array<string, string|bool> $parameters
+     */
+    public function testWhyCommandOutputs(array $parameters, string $expectedOutput): void
+    {
+        $packageToBeInspected = $parameters['package'];
+        $renderAsTree = $parameters['--tree'] ?? false;
+        $renderRecursively = $parameters['--recursive'] ?? false;
+
+        $this->initTempComposer([
+            'repositories' => [
+                'packages' => [
+                    'type' => 'package',
+                    'package' => [
+                        ['name' => 'vendor1/package1', 'version' => '1.3.0', 'require' => ['vendor1/package2' => '^2']],
+                        ['name' => 'vendor1/package2', 'version' => '2.3.0', 'require' => ['vendor1/package3' => '^1']],
+                        ['name' => 'vendor1/package3', 'version' => '2.1.0']
+                    ],
+                ],
+            ],
+            'require' => [
+                'vendor1/package2' => '1.3.0',
+                'vendor1/package3' => '2.3.0',
+            ],
+            'require-dev' => [
+                'vendor2/package1' => '2.*'
+            ]
+        ]);
+
+        $firstRequiredPackage = self::getPackage('vendor1/package1', '1.3.0');
+        $firstRequiredPackage->setRequires([
+            'vendor1/package2' => new Link(
+                'vendor1/package1',
+                'vendor1/package2',
+                new MatchAllConstraint(),
+                Link::TYPE_REQUIRE,
+                '^2'
+            )
+        ]);
+        $secondRequiredPackage = self::getPackage('vendor1/package2', '2.3.0');
+        $secondRequiredPackage->setRequires([
+            'vendor1/package3' => new Link(
+                'vendor1/package2',
+                'vendor1/package3',
+                new MatchAllConstraint(),
+                Link::TYPE_REQUIRE,
+                '^1'
+            )
+        ]);
+        $thirdRequiredPackage = self::getPackage('vendor1/package3', '2.1.0');
+        $someDevRequiredPackage = self::getPackage('vendor2/package1');
+        $this->createComposerLock(
+            [$firstRequiredPackage, $secondRequiredPackage, $thirdRequiredPackage],
+            [$someDevRequiredPackage]
+        );
+        $this->createInstalledJson(
+            [$firstRequiredPackage, $secondRequiredPackage, $thirdRequiredPackage],
+            [$someDevRequiredPackage]
+        );
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run([
+            'command' => 'why',
+            'package' => $packageToBeInspected,
+            '--tree' => $renderAsTree,
+            '--recursive' => $renderRecursively,
+            '--locked' => true
+        ]);
+
+        $appTester->assertCommandIsSuccessful();
+
+        $this->assertEquals(trim($expectedOutput), trim($appTester->getDisplay(true)));
+    }
+
+    /**
+     * @return Generator<string, array{array<string, string|bool>, string}>
+     */
+    public static function caseWhyProvider(): Generator
+    {
+        yield 'there is no installed package depending on the package' => [
+            ['package' => 'vendor1/package1'],
+            'There is no installed package depending on "vendor1/package1"'
+        ];
+
+        yield 'a nested package dependency' => [
+            ['package' => 'vendor1/package3'],
+            <<<OUTPUT
+__root__         -     requires vendor1/package3 (2.3.0) 
+vendor1/package2 2.3.0 requires vendor1/package3 (^1)
+OUTPUT
+        ];
+
+        yield 'a nested package dependency (tree mode)' => [
+            ['package' => 'vendor1/package3', '--tree' => true],
+            <<<OUTPUT
+vendor1/package3 2.1.0 
+|--__root__ (requires vendor1/package3 2.3.0)
+`--vendor1/package2 2.3.0 (requires vendor1/package3 ^1)
+   |--__root__ (requires vendor1/package2 1.3.0)
+   `--vendor1/package1 1.3.0 (requires vendor1/package2 ^2)
+OUTPUT
+        ];
+
+        yield 'a nested package dependency (recursive mode)' => [
+            ['package' => 'vendor1/package3', '--recursive' => true],
+            <<<OUTPUT
+__root__         -     requires vendor1/package2 (1.3.0) 
+vendor1/package1 1.3.0 requires vendor1/package2 (^2)    
+__root__         -     requires vendor1/package3 (2.3.0) 
+vendor1/package2 2.3.0 requires vendor1/package3 (^1)
+OUTPUT
+        ];
+
+        yield 'a simple package dev dependency' => [
+            ['package' => 'vendor2/package1'],
+            '__root__ - requires (for development) vendor2/package1 (2.*)'
+        ];
+    }
+
+    /**
+     * Test that it finishes successfully and show some expected outputs depending on different command parameters
+     *
+     * @covers       \Composer\Command\BaseDependencyCommand
+     * @covers       \Composer\Command\ProhibitsCommand
+     *
+     * @dataProvider caseWhyNotProvider
+     *
+     * @param array<string, string> $parameters
+     */
+    public function testWhyNotCommandOutputs(array $parameters, string $expectedOutput): void
+    {
+        $packageToBeInspected = $parameters['package'];
+        $packageVersionToBeInspected = $parameters['version'];
+
+        $this->initTempComposer([
+            'repositories' => [
+                'packages' => [
+                    'type' => 'package',
+                    'package' => [
+                        ['name' => 'vendor1/package1', 'version' => '1.3.0'],
+                        ['name' => 'vendor2/package1', 'version' => '2.0.0'],
+                        ['name' => 'vendor2/package2', 'version' => '1.0.0', 'require' => ['vendor2/package3' => '1.4.*']],
+                        ['name' => 'vendor2/package3', 'version' => '1.4.0'],
+                        ['name' => 'vendor2/package3', 'version' => '1.5.0']
+                    ],
+                ],
+            ],
+            'require' => [
+                'vendor1/package1' => '1.*'
+            ],
+            'require-dev' => [
+                'vendor2/package1' => '2.*',
+                'vendor2/package2' => '^1'
+            ]
+        ]);
+
+        $someRequiredPackage = self::getPackage('vendor1/package1', '1.3.0');
+        $firstDevRequiredPackage = self::getPackage('vendor2/package1', '2.0.0');
+        $secondDevRequiredPackage = self::getPackage('vendor2/package2', '1.0.0');
+        $secondDevRequiredPackage->setRequires([
+            'vendor2/package3' => new Link(
+                'vendor2/package2',
+                'vendor2/package3',
+                new MatchAllConstraint(),
+                Link::TYPE_REQUIRE,
+                '1.4.*'
+            )
+        ]);
+       $secondDevNestedRequiredPackage = self::getPackage('vendor2/package3', '1.4.0');
+
+        $this->createComposerLock(
+            [$someRequiredPackage], 
+            [$firstDevRequiredPackage, $secondDevRequiredPackage]
+        );
+        $this->createInstalledJson(
+            [$someRequiredPackage], 
+            [$firstDevRequiredPackage, $secondDevRequiredPackage, $secondDevNestedRequiredPackage]
+        );
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run([
+            'command' => 'why-not',
+            'package' => $packageToBeInspected,
+            'version' => $packageVersionToBeInspected
+        ]);
+
+        $appTester->assertCommandIsSuccessful();
+        $this->assertSame(trim($expectedOutput), trim($appTester->getDisplay(true)));
+    }
+
+    /**
+     * @return Generator<string, array{array<string, string>, string}>
+     */
+    public function caseWhyNotProvider(): Generator
+    {
+        yield 'it could not found the package with a specific version' => [
+            ['package' => 'vendor1/package1', 'version' => '3.*'],
+            <<<OUTPUT
+Package "vendor1/package1" could not be found with constraint "3.*", results below will most likely be incomplete.
+__root__ - requires vendor1/package1 (1.*) 
+Not finding what you were looking for? Try calling `composer update "vendor1/package1:3.*" --dry-run` to get another view on the problem.
+OUTPUT
+        ];
+
+        yield 'it could not found the package and there is no installed package with a specific version' => [
+            ['package' => 'vendor1/package1', 'version' => '^1.4'],
+            <<<OUTPUT
+Package "vendor1/package1" could not be found with constraint "^1.4", results below will most likely be incomplete.
+There is no installed package depending on "vendor1/package1" in versions not matching ^1.4
+Not finding what you were looking for? Try calling `composer update "vendor1/package1:^1.4" --dry-run` to get another view on the problem.
+OUTPUT
+        ];
+
+        yield 'there is no installed package depending on the package in versions not matching a specific version' => [
+            ['package' => 'vendor1/package1', 'version' => '^1.3'],
+            <<<OUTPUT
+There is no installed package depending on "vendor1/package1" in versions not matching ^1.3
+Not finding what you were looking for? Try calling `composer update "vendor1/package1:^1.3" --dry-run` to get another view on the problem.
+OUTPUT
+        ];
+
+        yield 'an installed package requires an incompatible version of the inspected package' => [
+            ['package' => 'vendor2/package3', 'version' => '1.5.0'],
+            <<<OUTPUT
+vendor2/package2 1.0.0 requires vendor2/package3 (1.4.*) 
+Not finding what you were looking for? Try calling `composer update "vendor2/package3:1.5.0" --dry-run` to get another view on the problem.
+OUTPUT
+        ];
+    }
+}