diff --git a/java-type-checker/.idea/misc.xml b/java-type-checker/.idea/misc.xml
index c24fcb0..a7ce7ea 100644
--- a/java-type-checker/.idea/misc.xml
+++ b/java-type-checker/.idea/misc.xml
@@ -12,5 +12,5 @@
       <entry name="!?*.clj" />
     </wildcardResourcePatterns>
   </component>
-  <component name="ProjectRootManager" version="2" project-jdk-name="Python 3" project-jdk-type="Python SDK" />
+  <component name="ProjectRootManager" version="2" project-jdk-name="Python 3 (/usr/local/bin/python3)" project-jdk-type="Python SDK" />
 </project>
\ No newline at end of file
diff --git a/java-type-checker/.idea/type-checker.iml b/java-type-checker/.idea/type-checker.iml
index 52e75c6..abd342a 100644
--- a/java-type-checker/.idea/type-checker.iml
+++ b/java-type-checker/.idea/type-checker.iml
@@ -2,7 +2,7 @@
 <module type="PYTHON_MODULE" version="4">
   <component name="NewModuleRootManager">
     <content url="file://$MODULE_DIR$" />
-    <orderEntry type="jdk" jdkName="Python 3" jdkType="Python SDK" />
+    <orderEntry type="jdk" jdkName="Python 3 (/usr/local/bin/python3)" jdkType="Python SDK" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
   <component name="TestRunnerService">
diff --git a/java-type-checker/java_type_checker/expressions.py b/java-type-checker/java_type_checker/expressions.py
index 27ed57e..9a494e7 100644
--- a/java-type-checker/java_type_checker/expressions.py
+++ b/java-type-checker/java_type_checker/expressions.py
@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-from .types import Type
+from .types import Type, NoSuchMethod
 
 
 class Expression(object):
@@ -31,6 +31,12 @@ def __init__(self, name, declared_type):
         self.name = name                    #: The name of the variable
         self.declared_type = declared_type  #: The declared type of the variable (Type)
 
+    def static_type(self):
+        return self.declared_type
+
+    def check_types(self):
+        pass
+
 
 class Literal(Expression):
     """ A literal value entered in the code, e.g. `5` in the expression `x + 5`.
@@ -39,22 +45,69 @@ def __init__(self, value, type):
         self.value = value  #: The literal value, as a string
         self.type = type    #: The type of the literal (Type)
 
+    def static_type(self):
+        return self.type
+
+    def check_types(self):
+        pass
+
+
 
 class NullLiteral(Literal):
     def __init__(self):
         super().__init__("null", Type.null)
 
+    def static_type(self):
+        return Type.null
+
+    def check_types(self):
+        pass
+
 
 class MethodCall(Expression):
     """
     A Java method invocation, i.e. `foo.bar(0, 1, 2)`.
     """
     def __init__(self, receiver, method_name, *args):
-        self.receiver = receiver
         self.receiver = receiver        #: The object whose method we are calling (Expression)
         self.method_name = method_name  #: The name of the method to call (String)
         self.args = args                #: The method arguments (list of Expressions)
 
+    def static_type(self):
+        return self.receiver.static_type().method_named(self.method_name).return_type
+
+    def check_types(self):
+        #check for the primitive error
+        if not self.receiver.static_type().is_instantiable:
+            raise JavaTypeError(
+                "Type {0} does not have methods".format(
+                    self.receiver.static_type().name))
+
+        method = self.receiver.static_type().method_named(self.method_name)
+        expected_argument_types = method.argument_types
+        numOfMethodParameters = len(method.argument_types)
+
+
+        #If the length of methods are not the same
+        if (len(self.args) != numOfMethodParameters):
+            raise JavaTypeError(
+                "Wrong number of arguments for {0}: expected {1}, got {2}".format(
+                    str(self.receiver.static_type().name) + "." + str(self.method_name) + "()",
+                    numOfMethodParameters,
+                    len(self.args)))
+
+        actual_argument_types = []
+        for i in range(len(self.args)):
+            actual_argument_types.append(self.args[i].static_type())
+
+        for i in range(len(expected_argument_types)):
+            if not actual_argument_types[i].is_subtype_of(expected_argument_types[i]):
+                raise JavaTypeError(
+                    "{0} expects arguments of type {1}, but got {2}".format(
+                        str(self.receiver.static_type().name) + "." + str(self.method_name) + "()",
+                        names(expected_argument_types),
+                        names(actual_argument_types)))
+
 
 class ConstructorCall(Expression):
     """
@@ -64,6 +117,38 @@ def __init__(self, instantiated_type, *args):
         self.instantiated_type = instantiated_type  #: The type to instantiate (Type)
         self.args = args                            #: Constructor arguments (list of Expressions)
 
+    def static_type(self):
+        return self.instantiated_type
+
+    def check_types(self):
+        #checking if it is the primitives types.
+        if not(self.instantiated_type.is_instantiable):
+            raise JavaTypeError(
+                "Type {0} is not instantiable".format(
+                    self.instantiated_type.name))
+
+        list_of_expected_constructor_arguments = self.instantiated_type.constructor.argument_types
+
+        if (len(self.args) != len(list_of_expected_constructor_arguments)):
+            raise JavaTypeError(
+                "Wrong number of arguments for {0} constructor: expected {1}, got {2}".format(
+                    self.instantiated_type.name,
+                    len(list_of_expected_constructor_arguments),
+                    len(self.args)
+                )
+            )
+
+        list_of_actual_argument_types = []
+        for i in range(len(self.args)):
+            list_of_actual_argument_types.append(self.args[i].static_type())
+
+        for i in range(len(list_of_expected_constructor_arguments)):
+            if not list_of_actual_argument_types[i].is_subtype_of(list_of_expected_constructor_arguments[i]):
+                raise JavaTypeError(
+                    "{0} constructor expects arguments of type {1}, but got {2}".format(
+                        self.instantiated_type.name,
+                        names(list_of_expected_constructor_arguments),
+                        names(list_of_actual_argument_types)))
 
 class JavaTypeError(Exception):
     """ Indicates a compile-time type error in an expression.
diff --git a/java-type-checker/java_type_checker/types.py b/java-type-checker/java_type_checker/types.py
index 465f7f4..d72c5df 100644
--- a/java-type-checker/java_type_checker/types.py
+++ b/java-type-checker/java_type_checker/types.py
@@ -12,7 +12,13 @@ def __init__(self, name, direct_supertypes=[]):
     def is_subtype_of(self, other):
         """ True if this type can be used where the other type is expected.
         """
-        return True  # TODO: implement
+        if (other is self):
+            return True
+        else:
+            for directsupertypes in self.direct_supertypes:
+                if (directsupertypes.is_subtype_of(other)):
+                    return True
+            return False
 
     def is_supertype_of(self, other):
         """ Convenience counterpart to is_subtype_of().
@@ -71,7 +77,7 @@ class NullType(Type):
     """
     def __init__(self):
         super().__init__("null")
-
+        self.is_instantiable = False
 
 class NoSuchMethod(Exception):
     pass
diff --git a/java-type-checker/tests/test_null.py b/java-type-checker/tests/test_null.py
index 36693c2..6de11cb 100644
--- a/java-type-checker/tests/test_null.py
+++ b/java-type-checker/tests/test_null.py
@@ -13,7 +13,7 @@ def test_object_params_accept_null(self):
         Equivalent Java:
 
             Rectangle rect;
-
+https://github.com/khintk/comp394-type-modeling
             rect.setFillColor(null);
         """
         self.assertNoCompileErrors(
@@ -22,6 +22,7 @@ def test_object_params_accept_null(self):
                 "setFillColor",
                 NullLiteral()))
 
+
     def test_cannot_call_method_on_null(self):
         """
         Equivalent Java:
diff --git a/java-type-checker/tests/test_type_checking.py b/java-type-checker/tests/test_type_checking.py
index b10ef24..d544433 100644
--- a/java-type-checker/tests/test_type_checking.py
+++ b/java-type-checker/tests/test_type_checking.py
@@ -8,15 +8,15 @@
 
 class TestTypeChecking(TypeTest):
 
-    def test_variables_never_have_type_errors(self):
+    def test_variables_never_have_type_errors(self): #Pass
         self.assertNoCompileErrors(
             Variable("p", Graphics.point))
 
-    def test_literals_never_have_type_errors(self):
+    def test_literals_never_have_type_errors(self): #Pass
         self.assertNoCompileErrors(
             Variable("3.72", Type.double))
 
-    def test_simple_method_call_passes(self):
+    def test_simple_method_call_passes(self): #pass
         """
         Equivalent Java:
 
@@ -29,7 +29,7 @@ def test_simple_method_call_passes(self):
                 Variable("p", Graphics.point),
                 "getX"))
 
-    def test_flags_nonexistent_method(self):
+    def test_flags_nonexistent_method(self): #Pass
         """
         Equivalent Java:
 
@@ -44,7 +44,7 @@ def test_flags_nonexistent_method(self):
                 Variable("p", Graphics.point),
                 "getZ"))
 
-    def test_flags_too_many_arguments(self):
+    def test_flags_too_many_arguments(self): #Pass
         """
         Equivalent Java:
 
@@ -61,7 +61,7 @@ def test_flags_too_many_arguments(self):
                 Literal("0.0", Type.double),
                 Literal("1.0", Type.double)))
 
-    def test_flags_too_few_arguments(self):
+    def test_flags_too_few_arguments(self): #Pass
         """
         Equivalent Java:
 
@@ -77,7 +77,7 @@ def test_flags_too_few_arguments(self):
                 "setPosition",
                 Literal("0.0", Type.double)))
 
-    def test_flags_wrong_argument_type(self):
+    def test_flags_wrong_argument_type(self): #Pass
         """
         Equivalent Java:
 
@@ -94,7 +94,7 @@ def test_flags_wrong_argument_type(self):
                 Literal("0.0", Type.double),
                 Literal("true", Type.boolean)))
 
-    def test_allows_subtypes_for_arguments(self):
+    def test_allows_subtypes_for_arguments(self): #Pass
         """
         Equivalent Java:
 
@@ -109,7 +109,7 @@ def test_allows_subtypes_for_arguments(self):
                 "setFillColor",
                 Variable("red", Graphics.color)))
 
-    def test_flags_wrong_number_of_constructor_arguments(self):
+    def test_flags_wrong_number_of_constructor_arguments(self): #Pass
         """
         Equivalent Java:
 
@@ -124,7 +124,7 @@ def test_flags_wrong_number_of_constructor_arguments(self):
                 Graphics.rectangle,
                 Variable("p", Graphics.point)))
 
-    def test_flags_wrong_constructor_argument_type(self):
+    def test_flags_wrong_constructor_argument_type(self): #Fail
         """
         Equivalent Java:
 
@@ -140,7 +140,7 @@ def test_flags_wrong_constructor_argument_type(self):
                 Variable("p", Graphics.point),
                 Literal("true", Type.boolean)))
 
-    def test_cannot_call_methods_on_primitives(self):
+    def test_cannot_call_methods_on_primitives(self): # Pass
         """
         Equivalent Java:
 
@@ -160,14 +160,14 @@ def test_cannot_call_methods_on_primitives(self):
 
             new int()
         """
-    def test_cannot_instantiate_primitives(self):
+    def test_cannot_instantiate_primitives(self): #Pass
         self.assertCompileError(
             JavaTypeError,
             "Type int is not instantiable",
             ConstructorCall(
                 Type.int))
 
-    def test_does_not_allow_void_passed_as_argument(self):
+    def test_does_not_allow_void_passed_as_argument(self): #Fail
         """
         Equivalent Java:
 
@@ -188,7 +188,7 @@ def test_does_not_allow_void_passed_as_argument(self):
                     "setStrokeColor",
                     Variable("red", Graphics.color))))
 
-    def test_passes_deep_expression(self):
+    def test_passes_deep_expression(self): #Fail
         """
         Equivalent Java:
 
@@ -213,7 +213,7 @@ def test_passes_deep_expression(self):
                         Variable("window", Graphics.window),
                         "getSize"))))
 
-    def test_catch_wrong_name_in_deep_expression(self):
+    def test_catch_wrong_name_in_deep_expression(self): #Fail
         """
         Equivalent Java:
 
diff --git a/python-attr-lookup/python-attr-lookup.iml b/python-attr-lookup/python-attr-lookup.iml
index 01e8e1b..c514cf2 100644
--- a/python-attr-lookup/python-attr-lookup.iml
+++ b/python-attr-lookup/python-attr-lookup.iml
@@ -9,12 +9,10 @@
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="module-library" scope="TEST">
-      <library name="JUnit5.0">
+      <library name="JUnit5">
         <CLASSES>
-          <root url="jar://$MAVEN_REPOSITORY$/org/junit/jupiter/junit-jupiter-api/5.0.0/junit-jupiter-api-5.0.0.jar!/" />
-          <root url="jar://$MAVEN_REPOSITORY$/org/apiguardian/apiguardian-api/1.0.0/apiguardian-api-1.0.0.jar!/" />
-          <root url="jar://$MAVEN_REPOSITORY$/org/opentest4j/opentest4j/1.0.0/opentest4j-1.0.0.jar!/" />
-          <root url="jar://$MAVEN_REPOSITORY$/org/junit/platform/junit-platform-commons/1.0.0/junit-platform-commons-1.0.0.jar!/" />
+          <root url="jar://$APPLICATION_HOME_DIR$/plugins/junit/lib/junit-jupiter-api-5.0.0-RC2.jar!/" />
+          <root url="jar://$APPLICATION_HOME_DIR$/plugins/junit/lib/opentest4j-1.0.0-RC1.jar!/" />
         </CLASSES>
         <JAVADOC />
         <SOURCES />
diff --git a/python-attr-lookup/src/plang/PythonObject.java b/python-attr-lookup/src/plang/PythonObject.java
index a8e311f..321bb27 100644
--- a/python-attr-lookup/src/plang/PythonObject.java
+++ b/python-attr-lookup/src/plang/PythonObject.java
@@ -1,10 +1,6 @@
 package plang;
 
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 
 /**
  * The runtime state of an object in Python.
@@ -51,7 +47,10 @@ public List<PythonObject> getMRO() {
      * result (i.e. it remembers the list buildMRO() returned and keeps returning it).
      */
     protected List<PythonObject> buildMRO() {
-        throw new UnsupportedOperationException("not implemented yet");
+        List<PythonObject> resultMRO = new ArrayList<>();
+        resultMRO.add(this); //adding the self
+        resultMRO.addAll(this.getType().getMRO()); //adding the subclasses
+        return resultMRO;
     }
 
     /**
@@ -62,8 +61,16 @@ protected List<PythonObject> buildMRO() {
      * @throws PythonAttributeException When there is no attribute on this object with that name.
      */
     public final PythonObject get(String attrName) throws PythonAttributeException {
-        throw new UnsupportedOperationException("not implemented yet");
-    }
+
+        List <PythonObject> mroresults = getMRO();
+        for (int i = 0; i < mroresults.size(); i++) {
+                if (mroresults.get(i).attrs.containsKey(attrName)) {
+                    return mroresults.get(i).attrs.get(attrName);
+                }
+            }
+            throw new PythonAttributeException(this, attrName);
+        }
+
 
     /**
      * Add or changes the value of an attribute on this object. Note that it sets the value for
@@ -73,8 +80,9 @@ public final PythonObject get(String attrName) throws PythonAttributeException {
      * @param attrName The name of the attribute to set
      * @param value Its new value
      */
+
     public final void set(String attrName, PythonObject value) {
-        throw new UnsupportedOperationException("not implemented yet");
+        this.attrs.put(attrName,value);
     }
 
     @Override
diff --git a/python-attr-lookup/src/plang/PythonType.java b/python-attr-lookup/src/plang/PythonType.java
index 4e2be4a..35b981e 100644
--- a/python-attr-lookup/src/plang/PythonType.java
+++ b/python-attr-lookup/src/plang/PythonType.java
@@ -19,6 +19,7 @@ public class PythonType extends PythonObject {
      *             (In real Python, instead of null it would be the class called `object`, and
      *             it would be a list instead of a single value.)
      */
+
     public PythonType(String name, PythonObject base) {
         super(null);  // In real Python, this would be the type called `type`
         this.name = name;
@@ -29,6 +30,7 @@ public PythonType(String name, PythonObject base) {
      * The name of this class.
      */
     public String getName() {
+
         return name;
     }
 
@@ -36,12 +38,18 @@ public String getName() {
      * The base type (superclass) of this class.
      */
     public PythonObject getBase() {
+
         return base;
     }
 
     @Override
     protected List<PythonObject> buildMRO() {
-        throw new UnsupportedOperationException("not implemented yet");
+        List<PythonObject> resultMRO = new ArrayList<>();
+        resultMRO.add(this);
+        if (this.getBase() != null){
+            resultMRO.addAll(this.getBase().getMRO());
+        }
+        return resultMRO;
     }
 
     /**
@@ -49,7 +57,8 @@ protected List<PythonObject> buildMRO() {
      * this PythonType.
      */
     public PythonObject instantiate() {
-        throw new UnsupportedOperationException("not implemented yet");
+        PythonObject instance = new PythonObject(this);
+        return instance;
     }
 
     @Override
diff --git a/python-attr-lookup/test/plang/PythonObjectTest.java b/python-attr-lookup/test/plang/PythonObjectTest.java
index 9fa0483..d813030 100644
--- a/python-attr-lookup/test/plang/PythonObjectTest.java
+++ b/python-attr-lookup/test/plang/PythonObjectTest.java
@@ -8,13 +8,13 @@
 
 import static org.junit.jupiter.api.Assertions.*;
 
+
 class PythonObjectTest {
 
     private PythonType fooType;
     private PythonType barType;
     private PythonObject foo;
     private PythonObject bar;
-
     /**
      * Equivalent Python:
      *
@@ -100,7 +100,7 @@ void objectsSupportNullValues() throws Exception {
         assertEquals(null, foo.get("worries"));  // No exception!
     }
 
-    @Test
+    @Test //didnt pass
     void findInheritedAttrs() throws Exception {
         // Equivalent Python:
         //
@@ -116,7 +116,7 @@ void findInheritedAttrs() throws Exception {
         assertEqualsPyStr("rainbow", bar.get("socks"));
     }
 
-    @Test
+    @Test //didnt pass
     void overrideInheritedAttrsInType() throws Exception {
         // Equivalent Python:
         //
@@ -132,7 +132,7 @@ void overrideInheritedAttrsInType() throws Exception {
         assertEqualsPyStr("polka dot", bar.get("socks"));
     }
 
-    @Test
+    @Test //didnt pass
     void overrideInheritedAttrsInInstance() throws Exception {
         // Equivalent Python:
         //
@@ -149,7 +149,7 @@ void overrideInheritedAttrsInInstance() throws Exception {
     }
 
 
-    @Test
+    @Test //didnt pass
     void overrideInheritedAttrsWithNull() throws Exception {
         // Equivalent Python:
         //