diff --git a/shared/build.gradle.kts b/shared/build.gradle.kts
index c1fa830..cc5d678 100644
--- a/shared/build.gradle.kts
+++ b/shared/build.gradle.kts
@@ -1,6 +1,12 @@
+val versions = mapOf(
+    "kotlinx-datetime" to "0.6.2"
+)
+
 plugins {
     alias(libs.plugins.kotlinMultiplatform)
     alias(libs.plugins.androidLibrary)
+    id("dev.mokkery") version "2.0.0"
+    kotlin("plugin.allopen") version "2.1.10"
 }
 
 kotlin {
@@ -25,7 +31,7 @@ kotlin {
 
     sourceSets {
         commonMain.dependencies {
-            //put your multiplatform dependencies here
+            implementation("org.jetbrains.kotlinx:kotlinx-datetime:${versions["kotlinx-datetime"]}")
         }
         commonTest.dependencies {
             implementation(libs.kotlin.test)
@@ -44,3 +50,8 @@ android {
         targetCompatibility = JavaVersion.VERSION_1_8
     }
 }
+
+allOpen {
+    annotation("com.tle.astrologylibrary.OpenForMokkery")
+    // annotations("com.another.Annotation", "com.third.Annotation")
+}
\ No newline at end of file
diff --git a/shared/src/commonMain/kotlin/com/tle/astrologylibrary/OpenForMokkery.kt b/shared/src/commonMain/kotlin/com/tle/astrologylibrary/OpenForMokkery.kt
new file mode 100644
index 0000000..f37a50d
--- /dev/null
+++ b/shared/src/commonMain/kotlin/com/tle/astrologylibrary/OpenForMokkery.kt
@@ -0,0 +1,3 @@
+package com.tle.astrologylibrary
+
+annotation class OpenForMokkery()
\ No newline at end of file
diff --git a/shared/src/commonMain/kotlin/com/tle/astrologylibrary/Subject.kt b/shared/src/commonMain/kotlin/com/tle/astrologylibrary/Subject.kt
new file mode 100644
index 0000000..512113b
--- /dev/null
+++ b/shared/src/commonMain/kotlin/com/tle/astrologylibrary/Subject.kt
@@ -0,0 +1,7 @@
+package com.tle.astrologylibrary
+
+@OpenForMokkery
+class A constructor()
+@OpenForMokkery
+class B constructor()
+class Subject(val a: A, val b: B)
\ No newline at end of file
diff --git a/shared/src/commonTest/kotlin/com/tle/astrologylibrary/SubjectTest.kt b/shared/src/commonTest/kotlin/com/tle/astrologylibrary/SubjectTest.kt
new file mode 100644
index 0000000..c655c8c
--- /dev/null
+++ b/shared/src/commonTest/kotlin/com/tle/astrologylibrary/SubjectTest.kt
@@ -0,0 +1,16 @@
+package com.tle.astrologylibrary
+
+import dev.mokkery.mock
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class SubjectTest {
+    @Test
+    fun testCreateSubject() {
+        val a = mock<A> {}
+        val b = mock<B> {}
+        val subject = Subject(a, b)
+        assertEquals(a, subject.a)
+        assertEquals(b, subject.b)
+    }
+}