Add Model.is to compare models with each other

src/Lucid/Model/index.js

@@ -780,6 +780,21 @@ class Model extends BaseModel {
     return evaluatedAttrs
   }
 
+  /**
+   * Checks if the passed model instance's record is the same as the current
+   *
+   * @method is
+   * @param  {Model} model
+   *
+   * @return {Boolean}
+   */
+  is (model) {
+    return !!model &&
+      this.primaryKeyValue === model.primaryKeyValue &&
+      this.constructor.table === model.constructor.table &&
+      this.constructor.connection === model.constructor.connection
+  }
+
   /**
    * Persist model instance to the database. It will create
    * a new row when model has not been persisted already,

test/unit/lucid.spec.js

@@ -113,6 +113,77 @@ test.group('Model', (group) => {
     assert.deepEqual(user.$attributes, { username: 'virk', age: 22 })
   })
 
+  test('can verify that two models hold the same record', (assert) => {
+    class User extends Model {}
+
+    const user = new User()
+    user.id = 1
+    const user2 = new User()
+    user2.id = 1
+
+    assert.isTrue(user.is(user2))
+  })
+
+  test('can verify that two models do not hold the same record based on primary key', (assert) => {
+    class User extends Model {}
+
+    const user = new User()
+    user.id = 1
+    const user2 = new User()
+    user2.id = 2
+
+    assert.isFalse(user.is(user2))
+  })
+
+  test('can verify that two models do not hold the same record when comparing against an empty model', (assert) => {
+    class User extends Model {}
+
+    const user = new User()
+
+    assert.isFalse(user.is(null))
+  })
+
+  test('can verify that two models do not hold the same record based on table', (assert) => {
+    class User extends Model {}
+    class Post extends Model {}
+
+    const user = new User()
+    user.id = 1
+    const post = new Post()
+    post.id = 1
+
+    assert.isFalse(user.is(post))
+  })
+
+  test('can verify that two models do not hold the same record based on connection', (assert) => {
+    class SqliteUser extends Model {
+      static get connection () {
+        return 'sqlite'
+      }
+
+      static get table () {
+        return 'user'
+      }
+    }
+
+    class MysqlUser extends Model {
+      static get connection () {
+        return 'mysql'
+      }
+
+      static get table () {
+        return 'user'
+      }
+    }
+
+    const user = new SqliteUser()
+    user.id = 1
+    const user2 = new MysqlUser()
+    user2.id = 1
+
+    assert.isFalse(user.is(user2))
+  })
+
   test('remove existing attributes when calling fill', (assert) => {
     class User extends Model {
     }