diff --git a/tests/+did/+unittest/test_document.m b/tests/+did/+unittest/test_document.m
new file mode 100644
index 0000000..53eb320
--- /dev/null
+++ b/tests/+did/+unittest/test_document.m
@@ -0,0 +1,45 @@
+classdef test_document < matlab.unittest.TestCase
+    methods (Test)
+        function test_dependency_management(testCase)
+            % Create a document of type 'demoC', which has 'depends_on' fields
+            doc = did.document('demoC');
+
+            % Verify 'depends_on' field exists
+            testCase.verifyTrue(isfield(doc.document_properties, 'depends_on'), ...
+                "The 'depends_on' field should exist for 'demoC' document type.");
+
+            % Test setting a new dependency value
+            doc = doc.set_dependency_value('item1', 'new_value');
+            retrieved_value = doc.dependency_value('item1');
+            testCase.verifyEqual(retrieved_value, 'new_value', ...
+                "Failed to set and retrieve a new dependency value.");
+
+            % Test updating an existing dependency value
+            doc = doc.set_dependency_value('item1', 'updated_value');
+            retrieved_value = doc.dependency_value('item1');
+            testCase.verifyEqual(retrieved_value, 'updated_value', ...
+                "Failed to update an existing dependency value.");
+        end
+
+        function test_file_management(testCase)
+            % Create a document of type 'demoFile', which is defined to handle files
+            doc = did.document('demoFile');
+
+            % Add a file and verify it was added
+            doc = doc.add_file('filename1.ext', '/path/to/file1.txt');
+            [isIn, ~, fI_index] = doc.is_in_file_list('filename1.ext');
+            testCase.verifyTrue((isIn==1)||(isIn==true), "File 'filename1.ext' should be in the file list.");
+            testCase.verifyNotEmpty(fI_index, "File info index should not be empty after adding a file.");
+
+            % Verify the location of the added file
+            testCase.verifyEqual(doc.document_properties.files.file_info(fI_index).locations.location, '/path/to/file1.txt', ...
+                "The location of the added file is incorrect.");
+
+            % Remove the file and verify it was removed
+            doc = doc.remove_file('filename1.ext');
+            [~, ~, fI_index_after_removal] = doc.is_in_file_list('filename1.ext');
+            % After removal, searching for the file info should yield an empty index
+            testCase.verifyEmpty(fI_index_after_removal, "File info should be empty after removing the file.");
+        end
+    end
+end
diff --git a/tests/+did/+unittest/test_fileobj.m b/tests/+did/+unittest/test_fileobj.m
new file mode 100644
index 0000000..99305b3
--- /dev/null
+++ b/tests/+did/+unittest/test_fileobj.m
@@ -0,0 +1,21 @@
+classdef test_fileobj < matlab.unittest.TestCase
+    methods (Test)
+        function test_constructor(testCase)
+            % Test creating a fileobj
+            theFileObj = did.file.fileobj();
+            testCase.verifyEqual(theFileObj.fid, -1);
+            testCase.verifyEqual(theFileObj.permission, 'r');
+            testCase.verifyEqual(theFileObj.machineformat, 'n');
+            testCase.verifyEqual(theFileObj.fullpathfilename, '');
+        end
+
+        function test_custom_file_handler_error(testCase)
+            % Test that passing customFileHandler to the constructor throws an error
+            my_handler = @(x) disp(['File operation: ' x]);
+
+            testCase.verifyError(@() did.file.fileobj('customFileHandler', my_handler), ...
+                'MATLAB:TooManyInputs', ...
+                'The constructor should throw a standard parser error for an unmatched parameter.');
+        end
+    end
+end
diff --git a/tests/+did/+unittest/test_query.m b/tests/+did/+unittest/test_query.m
new file mode 100644
index 0000000..c5ee84c
--- /dev/null
+++ b/tests/+did/+unittest/test_query.m
@@ -0,0 +1,44 @@
+classdef test_query < matlab.unittest.TestCase
+    methods (Test)
+        function test_creation(testCase)
+            % Test creating a query
+            q = did.query('base.name', 'exact_string', 'myname');
+            testCase.verifyEqual(q.searchstructure.field, 'base.name');
+            testCase.verifyEqual(q.searchstructure.operation, 'exact_string');
+            testCase.verifyEqual(q.searchstructure.param1, 'myname');
+        end
+
+        function test_invalid_operator(testCase)
+            % Test that an invalid operator throws an error
+            testCase.verifyError(@() did.query('base.name', 'invalid_op', 'myname'), 'MATLAB:validators:mustBeMember');
+        end
+
+        function test_and_query(testCase)
+            % Test combining queries with AND
+            q1 = did.query('base.name', 'exact_string', 'myname');
+            q2 = did.query('base.age', 'greaterthan', 30);
+            q_and = q1 & q2;
+            testCase.verifyEqual(numel(q_and.searchstructure), 2);
+            testCase.verifyEqual(q_and.searchstructure(1).field, 'base.name');
+            testCase.verifyEqual(q_and.searchstructure(1).operation, 'exact_string');
+            testCase.verifyEqual(q_and.searchstructure(1).param1, 'myname');
+            testCase.verifyEqual(q_and.searchstructure(2).field, 'base.age');
+            testCase.verifyEqual(q_and.searchstructure(2).operation, 'greaterthan');
+            testCase.verifyEqual(q_and.searchstructure(2).param1, 30);
+        end
+
+        function test_or_query(testCase)
+            % Test combining queries with OR
+            q1 = did.query('base.name', 'exact_string', 'myname');
+            q2 = did.query('base.age', 'greaterthan', 30);
+            q_or = q1 | q2;
+            testCase.verifyEqual(q_or.searchstructure.operation, 'or');
+            testCase.verifyEqual(q_or.searchstructure.param1(1).field, 'base.name');
+            testCase.verifyEqual(q_or.searchstructure.param1(1).operation, 'exact_string');
+            testCase.verifyEqual(q_or.searchstructure.param1(1).param1, 'myname');
+            testCase.verifyEqual(q_or.searchstructure.param2(1).field, 'base.age');
+            testCase.verifyEqual(q_or.searchstructure.param2(1).operation, 'greaterthan');
+            testCase.verifyEqual(q_or.searchstructure.param2(1).param1, 30);
+        end
+    end
+end