diff --git a/composer.json b/composer.json
index 1fde1c78a15f..9eeabe5eeea8 100644
--- a/composer.json
+++ b/composer.json
@@ -35,5 +35,7 @@
 			"type": "path",
 			"url": "./packages/*"
 		}
-	]
+	],
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/composer.lock b/composer.lock
index 32c672de1bab..7fb81dae8dab 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,7 +4,7 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "b711e37a57a39e3470c4af334eab9c50",
+    "content-hash": "49dfae78b865b05e4de33278963c050b",
     "packages": [
         {
             "name": "automattic/jetpack-asset-tools",
@@ -30,11 +30,11 @@
         },
         {
             "name": "automattic/jetpack-connection",
-            "version": "1.0.0",
+            "version": "dev-master",
             "dist": {
                 "type": "path",
                 "url": "./packages/connection",
-                "reference": "ca7edb2022bf0c5b1e045a2ad5d2c5229c364a4f"
+                "reference": "eb2ab1a317d710fbe651a20fa580d523e303d848"
             },
             "require": {
                 "automattic/jetpack-constants": "@dev",
@@ -95,20 +95,29 @@
             "dist": {
                 "type": "path",
                 "url": "./packages/jitm",
-                "reference": "de0110b1cce11fd0728ec3d8fcd03d457239354a"
+                "reference": "853d6934703fce515f16d5f3450cbb51ed05d09e"
             },
             "require": {
                 "automattic/jetpack-asset-tools": "@dev",
-                "automattic/jetpack-connection": "^1.0",
+                "automattic/jetpack-connection": "@dev",
                 "automattic/jetpack-constants": "@dev",
                 "automattic/jetpack-logo": "@dev"
             },
+            "require-dev": {
+                "phpunit/phpunit": "^5.7 || ^6.5 || ^7.5"
+            },
             "type": "library",
             "autoload": {
                 "psr-4": {
                     "Automattic\\Jetpack\\JITM\\": "src/"
                 }
             },
+            "scripts": {
+                "phpunit": [
+                    "@composer install",
+                    "./vendor/phpunit/phpunit/phpunit --colors=always"
+                ]
+            },
             "license": [
                 "GPL-2.0-or-later"
             ],
@@ -122,22 +131,12 @@
                 "url": "./packages/logo",
                 "reference": "aa3d128c9280d6186210a86b10f8bf5403f44be7"
             },
-            "require-dev": {
-                "php-mock/php-mock": "^2.1",
-                "phpunit/phpunit": "^5.7 || ^6.5 || ^7.5"
-            },
             "type": "library",
             "autoload": {
                 "psr-4": {
                     "Automattic\\Jetpack\\Assets\\": "src/"
                 }
             },
-            "scripts": {
-                "phpunit": [
-                    "@composer install",
-                    "./vendor/phpunit/phpunit/phpunit --colors=always"
-                ]
-            },
             "license": [
                 "GPL-2.0-or-later"
             ],
@@ -685,7 +684,7 @@
         }
     ],
     "aliases": [],
-    "minimum-stability": "stable",
+    "minimum-stability": "dev",
     "stability-flags": {
         "automattic/jetpack-connection": 20,
         "automattic/jetpack-options": 20,
@@ -695,7 +694,7 @@
         "automattic/jetpack-asset-tools": 20,
         "automattic/jetpack-autoloader": 20
     },
-    "prefer-stable": false,
+    "prefer-stable": true,
     "prefer-lowest": false,
     "platform": {
         "ext-openssl": "*"
diff --git a/packages/asset-tools/composer.json b/packages/asset-tools/composer.json
index 14b8ef5a7081..ae65a53d97fa 100644
--- a/packages/asset-tools/composer.json
+++ b/packages/asset-tools/composer.json
@@ -16,5 +16,7 @@
 			"type": "path",
 			"url": "../*"
 		}
-	]
+	],
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/autoloader/composer.json b/packages/autoloader/composer.json
index 2a6bba463fa6..a96cfeff9739 100644
--- a/packages/autoloader/composer.json
+++ b/packages/autoloader/composer.json
@@ -13,5 +13,7 @@
 	},
 	"extra": {
 		"class": "Automattic\\Jetpack\\Autoloader\\CustomAutoloaderPlugin"
-	}
+	},
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/connection/composer.json b/packages/connection/composer.json
index 3c8f2f566597..1f75092bf68a 100644
--- a/packages/connection/composer.json
+++ b/packages/connection/composer.json
@@ -3,7 +3,6 @@
 	"description": "Everything needed to connect to the Jetpack infrastructure",
 	"type": "library",
 	"license": "GPL-2.0-or-later",
-	"version": "1.0.0",
 	"require": {
 		"automattic/jetpack-constants": "@dev",
 		"automattic/jetpack-options": "@dev"
@@ -28,5 +27,7 @@
 			"type": "path",
 			"url": "../*"
 		}
-	]
+	],
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/constants/composer.json b/packages/constants/composer.json
index 0c09306ea3be..cb11ce4ddbf9 100644
--- a/packages/constants/composer.json
+++ b/packages/constants/composer.json
@@ -17,5 +17,7 @@
 			"@composer install",
 			"./vendor/phpunit/phpunit/phpunit --colors=always"
 		]
-	}
+	},
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/jitm/composer.json b/packages/jitm/composer.json
index f101fd1cb870..397327f7ffb9 100644
--- a/packages/jitm/composer.json
+++ b/packages/jitm/composer.json
@@ -5,10 +5,14 @@
 	"license": "GPL-2.0-or-later",
 	"require": {
 		"automattic/jetpack-asset-tools": "@dev",
-		"automattic/jetpack-connection": "^1.0",
+		"automattic/jetpack-connection": "@dev",
 		"automattic/jetpack-logo": "@dev",
 		"automattic/jetpack-constants": "@dev"
 	},
+	"require-dev": {
+		"phpunit/phpunit": "^5.7 || ^6.5 || ^7.5",
+		"php-mock/php-mock": "^2.1"
+	},
 	"autoload": {
 		"psr-4": {
 			"Automattic\\Jetpack\\JITM\\": "src/"
@@ -19,5 +23,13 @@
 			"type": "path",
 			"url": "../*"
 		}
-	]
+	],
+	"scripts": {
+		"phpunit": [
+			"@composer install",
+			"./vendor/phpunit/phpunit/phpunit --colors=always"
+		]
+	},
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/jitm/phpunit.xml.dist b/packages/jitm/phpunit.xml.dist
new file mode 100644
index 000000000000..443d8a0ace77
--- /dev/null
+++ b/packages/jitm/phpunit.xml.dist
@@ -0,0 +1,7 @@
+<phpunit bootstrap="tests/php/bootstrap.php" backupGlobals="false" colors="true">
+	<testsuites>
+		<testsuite name="main">
+			<directory prefix="test" suffix=".php">tests/php</directory>
+		</testsuite>
+	</testsuites>
+</phpunit>
diff --git a/packages/jitm/tests/php/bootstrap.php b/packages/jitm/tests/php/bootstrap.php
new file mode 100644
index 000000000000..48b34a7a581b
--- /dev/null
+++ b/packages/jitm/tests/php/bootstrap.php
@@ -0,0 +1,3 @@
+<?php
+
+require_once __DIR__ . '/../../vendor/autoload.php';
diff --git a/packages/jitm/tests/php/test_Manager.php b/packages/jitm/tests/php/test_Manager.php
new file mode 100644
index 000000000000..ce7ba7f65977
--- /dev/null
+++ b/packages/jitm/tests/php/test_Manager.php
@@ -0,0 +1,67 @@
+<?php
+
+namespace Automattic\Jetpack\JITM;
+
+use Automattic\Jetpack\JITM\Manager as Jetpack_JITM;
+use phpmock\functions\FunctionProvider;
+use phpmock\Mock;
+use phpmock\MockBuilder;
+use PHPUnit\Framework\TestCase;
+
+class Test_Jetpack_JITM extends TestCase {
+	public function setUp() {
+		$builder = new MockBuilder();
+		$builder->setNamespace( __NAMESPACE__ )
+			->setName( 'add_action' )
+			->setFunction( function() {} );
+		$builder->build()->enable();
+	}
+
+	public function tearDown() {
+		Mock::disableAll();
+	}
+
+	public function test_jitm_disabled_by_filter() {
+		$this->mock_filters( array(
+			array( 'jetpack_just_in_time_msgs', false, false ),
+		) );
+
+		$this->assertFalse( Jetpack_JITM::init() );
+
+		$this->clear_mock_filters();
+	}
+
+	public function test_jitm_enabled_by_default() {
+		$this->mock_filters( array(
+			array( 'jetpack_just_in_time_msgs', false, true ),
+		) );
+
+		$this->assertTrue( ! ! Jetpack_JITM::init() );
+
+		$this->clear_mock_filters();
+	}
+
+	protected function mock_filters( $filters ) {
+		$this->mocked_filters = $filters;
+		$builder = new MockBuilder();
+		$builder->setNamespace( __NAMESPACE__ )
+			->setName( 'apply_filters' )
+			->setFunction(
+				function() {
+					$current_args = func_get_args();
+					foreach ( $this->mocked_filters as $filter ) {
+						if ( array_slice( $filter, 0, -1 ) === $current_args ) {
+							return array_pop( $filter );
+						}
+					}
+				}
+			);
+		$this->apply_filters_mock = $builder->build();
+		$this->apply_filters_mock->enable();
+	}
+
+	protected function clear_mock_filters() {
+		$this->apply_filters_mock->disable();
+		unset( $this->mocked_filters );
+	}
+}
diff --git a/packages/logo/composer.json b/packages/logo/composer.json
index df975ad7d09a..104c0d931246 100644
--- a/packages/logo/composer.json
+++ b/packages/logo/composer.json
@@ -18,5 +18,7 @@
 			"@composer install",
 			"./vendor/phpunit/phpunit/phpunit --colors=always"
 		]
-	}
+	},
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/packages/options/composer.json b/packages/options/composer.json
index c63a531ae653..0058727beea5 100644
--- a/packages/options/composer.json
+++ b/packages/options/composer.json
@@ -20,5 +20,7 @@
 			"type": "path",
 			"url": "../*"
 		}
-	]
+	],
+	"minimum-stability": "dev",
+	"prefer-stable": true
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 41d345b9a9c9..25961d4346fc 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -75,9 +75,6 @@
 		<testsuite name="idc">
 			<file>tests/php/test_class.jetpack-idc.php</file>
 		</testsuite>
-		<testsuite name="jitm">
-			<file>tests/php/test_class.jetpack-jitm.php</file>
-		</testsuite>
 		<testsuite name="affiliate">
 			<file>tests/php/test_class.jetpack-affiliate.php</file>
 		</testsuite>
diff --git a/tests/php/test_class.jetpack-jitm.php b/tests/php/test_class.jetpack-jitm.php
deleted file mode 100644
index e60bcba8003b..000000000000
--- a/tests/php/test_class.jetpack-jitm.php
+++ /dev/null
@@ -1,14 +0,0 @@
-<?php
-
-use Automattic\Jetpack\JITM\Manager as Jetpack_JITM;
-
-class WP_Test_Jetpack_JITM extends WP_UnitTestCase {
-	function test_jitm_disabled_by_filter() {
-		add_filter( 'jetpack_just_in_time_msgs', '__return_false', 50 );
-		$this->assertFalse( Jetpack_JITM::init() );
-	}
-
-	function test_jitm_enabled_by_default() {
-		$this->assertTrue( ! ! Jetpack_JITM::init() );
-	}
-}