diff --git a/test/Unit/test_manifest_validation.gd b/test/Unit/test_manifest_validation.gd
new file mode 100644
index 00000000..b25a22f5
--- /dev/null
+++ b/test/Unit/test_manifest_validation.gd
@@ -0,0 +1,88 @@
+extends GutTest
+
+
+var test_is_mod_id_valid_params = [
+	["abc-abc", true],
+	["abcdefg-abcdefg", true],
+	["abc-abcdefg", true],
+	["ABC-AB_CDE", true],
+	["123-123", true],
+
+	["abc-abc-abc", false],
+	["abcdef-", false],
+	["-abcdef", false],
+	["a-bcdef", false],
+	["abcdef", false],
+	["a", false],
+	["abc-%ab", false],
+]
+
+# Test with distinct mod ids in arrays
+# Test with overlapping mod ids in arrays
+# Test with no mod ids in one array
+# Test with no mod ids in both arrays
+var test_validate_distinct_mod_ids_in_arrays_params = [
+	[["mod1-mod1", "mod2-mod2", "mod3-mod3"], ["mod4-mod4", "mod5-mod5", "mod6-mod6"], true],
+	[["mod1-mod1", "mod2-mod2", "mod3-mod3"], ["mod4-mod4", "mod5-mod5", "mod6-mod6", "mod2-mod2"], false],
+	[[], ["mod4-mod4", "mod5-mod5", "mod6-mod6"], true],
+	[["mod1-mod1", "mod2-mod2", "mod3-mod3"], [], true],
+	[[], [], true],
+]
+
+# Test with a valid mod id array
+# Test with an invalid mod id array
+var test_is_mod_id_array_valid_params = [
+	[["mod1-mod1", "mod2-mod2", "mod3-mod3"], true],
+	[["mod1-mod1", "mod2-mod2", "invalid-mod21###"], false],
+]
+
+
+func test_is_mod_id_valid(params = use_parameters(test_is_mod_id_valid_params)) -> void:
+	# prepare
+	var mod_id = params[0]
+	var expected_result = params[1]
+
+	# test
+	var result = ModManifest.is_mod_id_valid(mod_id, mod_id, "", true)
+
+	# validate
+	assert_true(
+		result == expected_result,
+		"Expected %s but was %s instead for mod_id \"%s\"" % [expected_result, result, mod_id]
+	)
+
+
+func test_validate_distinct_mod_ids_in_arrays(params = use_parameters(test_validate_distinct_mod_ids_in_arrays_params)) -> void:
+	# prepare
+	var mod_id = "test-mod"
+	var array_one = params[0]
+	var array_two = params[1]
+	var array_description = ["array_one", "array_two"]
+	var additional_info = "additional info"
+	var expected_result = params[2]
+
+	# test
+	var result = ModManifest.validate_distinct_mod_ids_in_arrays(mod_id, array_one, array_two, array_description, additional_info, true)
+
+	# validate
+	assert_true(
+		result == expected_result,
+		"Expected %s but was %s instead for this arrays \"%s\" - \"%s\"" % [expected_result, result, array_one, array_two]
+	)
+
+
+func test_is_mod_id_array_valid(params = use_parameters(test_is_mod_id_array_valid_params)) -> void:
+	# prepare
+	var mod_id = "test-mod"
+	var mod_id_array = params[0]
+	var description = "array_description"
+	var expected_result = params[1]
+
+	# test
+	var result = ModManifest.is_mod_id_array_valid(mod_id, mod_id_array, description, true)
+
+	# validate
+	assert_true(
+		result == expected_result,
+		"Expected %s but was %s instead for this array \"%s\"" % [expected_result, result, mod_id_array]
+	)