Fix TabBar initialization issue and add tests

1 files changed, 671 insertions, 0 deletions

diff --git a/tests/scene/test_tab_container.h b/tests/scene/test_tab_container.h
new file mode 100644
index 0000000000..2a211a2c09
--- /dev/null
+++ b/tests/scene/test_tab_container.h
@@ -0,0 +1,671 @@
+/**************************************************************************/
+/*  test_tab_container.h                                                  */
+/**************************************************************************/
+/*                         This file is part of:                          */
+/*                             GODOT ENGINE                               */
+/*                        https://godotengine.org                         */
+/**************************************************************************/
+/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
+/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
+/*                                                                        */
+/* Permission is hereby granted, free of charge, to any person obtaining  */
+/* a copy of this software and associated documentation files (the        */
+/* "Software"), to deal in the Software without restriction, including    */
+/* without limitation the rights to use, copy, modify, merge, publish,    */
+/* distribute, sublicense, and/or sell copies of the Software, and to     */
+/* permit persons to whom the Software is furnished to do so, subject to  */
+/* the following conditions:                                              */
+/*                                                                        */
+/* The above copyright notice and this permission notice shall be         */
+/* included in all copies or substantial portions of the Software.        */
+/*                                                                        */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,        */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF     */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. */
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY   */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,   */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE      */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                 */
+/**************************************************************************/
+
+#ifndef TEST_TAB_CONTAINER_H
+#define TEST_TAB_CONTAINER_H
+
+#include "scene/gui/tab_container.h"
+
+#include "tests/test_macros.h"
+
+namespace TestTabContainer {
+static inline Array build_array() {
+	return Array();
+}
+template <typename... Targs>
+static inline Array build_array(Variant item, Targs... Fargs) {
+	Array a = build_array(Fargs...);
+	a.push_front(item);
+	return a;
+}
+
+TEST_CASE("[SceneTree][TabContainer] tab operations") {
+	TabContainer *tab_container = memnew(TabContainer);
+	SceneTree::get_singleton()->get_root()->add_child(tab_container);
+	MessageQueue::get_singleton()->flush();
+	SIGNAL_WATCH(tab_container, "tab_selected");
+	SIGNAL_WATCH(tab_container, "tab_changed");
+
+	Control *tab0 = memnew(Control);
+	tab0->set_name("tab0");
+	Control *tab1 = memnew(Control);
+	tab1->set_name("tab1");
+	Control *tab2 = memnew(Control);
+	tab2->set_name("tab2");
+
+	SUBCASE("[TabContainer] add tabs by adding children") {
+		CHECK(tab_container->get_tab_count() == 0);
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		// Add first tab child.
+		tab_container->add_child(tab0);
+		// MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(0)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(0)));
+
+		// Add second tab child.
+		tab_container->add_child(tab1);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// Check default values, the title is the name of the child.
+		CHECK(tab_container->get_tab_control(0) == tab0);
+		CHECK(tab_container->get_tab_idx_from_control(tab0) == 0);
+		CHECK(tab_container->get_tab_title(0) == "tab0");
+		CHECK(tab_container->get_tab_tooltip(0) == "");
+		CHECK_FALSE(tab_container->is_tab_disabled(0));
+		CHECK_FALSE(tab_container->is_tab_hidden(0));
+
+		CHECK(tab_container->get_tab_control(1) == tab1);
+		CHECK(tab_container->get_tab_idx_from_control(tab1) == 1);
+		CHECK(tab_container->get_tab_title(1) == "tab1");
+		CHECK(tab_container->get_tab_tooltip(1) == "");
+		CHECK_FALSE(tab_container->is_tab_disabled(1));
+		CHECK_FALSE(tab_container->is_tab_hidden(1));
+	}
+
+	SUBCASE("[TabContainer] remove tabs by removing children") {
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_DISCARD("tab_selected");
+		SIGNAL_DISCARD("tab_changed");
+
+		// Remove first tab.
+		tab_container->remove_child(tab0);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_tab_title(0) == "tab1");
+		CHECK(tab_container->get_tab_title(1) == "tab2");
+		CHECK(tab_container->get_tab_idx_from_control(tab1) == 0);
+		CHECK(tab_container->get_tab_idx_from_control(tab2) == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// Remove last tab.
+		tab_container->remove_child(tab2);
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_tab_title(0) == "tab1");
+		CHECK(tab_container->get_tab_idx_from_control(tab1) == 0);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// Remove only tab.
+		tab_container->remove_child(tab1);
+		CHECK(tab_container->get_tab_count() == 0);
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK("tab_changed", build_array(build_array(-1)));
+
+		// Remove current tab when there are other tabs.
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		tab_container->set_current_tab(1);
+		tab_container->set_current_tab(2);
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 2);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_DISCARD("tab_selected");
+		SIGNAL_DISCARD("tab_changed");
+
+		tab_container->remove_child(tab2);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+	}
+
+	SUBCASE("[TabContainer] move tabs by moving children") {
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_DISCARD("tab_selected");
+		SIGNAL_DISCARD("tab_changed");
+
+		// Move the first tab to the end.
+		tab_container->move_child(tab0, 2);
+		CHECK(tab_container->get_tab_idx_from_control(tab0) == 2);
+		CHECK(tab_container->get_tab_idx_from_control(tab1) == 0);
+		CHECK(tab_container->get_tab_idx_from_control(tab2) == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == 2);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// Move the second tab to the front.
+		tab_container->move_child(tab2, 0);
+		CHECK(tab_container->get_tab_idx_from_control(tab0) == 2);
+		CHECK(tab_container->get_tab_idx_from_control(tab1) == 1);
+		CHECK(tab_container->get_tab_idx_from_control(tab2) == 0);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 2);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+	}
+
+	SUBCASE("[TabContainer] set current tab") {
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(0)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(0)));
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Set the current tab.
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Set to same tab.
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK_FALSE("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Out of bounds.
+		ERR_PRINT_OFF;
+		tab_container->set_current_tab(-5);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		tab_container->set_current_tab(5);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+		ERR_PRINT_ON;
+	}
+
+	SUBCASE("[TabContainer] change current tab by changing visibility of children") {
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		SIGNAL_DISCARD("tab_selected");
+		SIGNAL_DISCARD("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Show a child to make it the current tab.
+		tab1->show();
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Hide the visible child to select the next tab.
+		tab1->hide();
+		CHECK(tab_container->get_current_tab() == 2);
+		CHECK(tab_container->get_previous_tab() == 1);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(2)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(2)));
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+		CHECK(tab2->is_visible());
+
+		// Hide the visible child to select the previous tab if there is no next.
+		tab2->hide();
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 2);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+
+		// Cannot hide if there is only one valid child since deselection is not enabled.
+		tab_container->remove_child(tab1);
+		tab_container->remove_child(tab2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_DISCARD("tab_selected");
+		SIGNAL_DISCARD("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+
+		tab0->hide();
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+
+		// Can hide the last tab if deselection is enabled.
+		tab_container->set_deselect_enabled(true);
+		tab0->hide();
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(-1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(-1)));
+		MessageQueue::get_singleton()->flush();
+		CHECK_FALSE(tab0->is_visible());
+	}
+
+	SIGNAL_UNWATCH(tab_container, "tab_selected");
+	SIGNAL_UNWATCH(tab_container, "tab_changed");
+
+	memdelete(tab2);
+	memdelete(tab1);
+	memdelete(tab0);
+	memdelete(tab_container);
+}
+
+TEST_CASE("[SceneTree][TabContainer] initialization") {
+	TabContainer *tab_container = memnew(TabContainer);
+
+	Control *tab0 = memnew(Control);
+	tab0->set_name("tab0");
+	Control *tab1 = memnew(Control);
+	tab1->set_name("tab1 ");
+	Control *tab2 = memnew(Control);
+	tab2->set_name("tab2    ");
+
+	SIGNAL_WATCH(tab_container, "tab_selected");
+	SIGNAL_WATCH(tab_container, "tab_changed");
+
+	SUBCASE("[TabContainer] add children before entering tree") {
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		tab_container->add_child(tab0);
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		tab_container->add_child(tab1);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		SceneTree::get_singleton()->get_root()->add_child(tab_container);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		CHECK(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+	}
+
+	SUBCASE("[TabContainer] current tab can be set before children are added") {
+		// Set the current tab before there are any tabs.
+		// This queues the current tab to update on entering the tree.
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		tab_container->add_child(tab0);
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		tab_container->add_child(tab1);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		tab_container->add_child(tab2);
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// Current tab is set when entering the tree.
+		SceneTree::get_singleton()->get_root()->add_child(tab_container);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+	}
+
+	SUBCASE("[TabContainer] cannot set current tab to an invalid value before tabs are set") {
+		tab_container->set_current_tab(100);
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		tab_container->add_child(tab0);
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		tab_container->add_child(tab1);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+
+		// This will print an error message as if `set_current_tab` was called after.
+		ERR_PRINT_OFF;
+		SceneTree::get_singleton()->get_root()->add_child(tab_container);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		ERR_PRINT_ON;
+	}
+
+	SUBCASE("[TabContainer] children visibility before entering tree") {
+		CHECK(tab_container->get_current_tab() == -1);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		// Adding a hidden child first will change visibility because it is the current tab.
+		tab0->hide();
+		tab_container->add_child(tab0);
+		CHECK(tab_container->get_tab_count() == 1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+
+		// Adding a visible child after will hide it because it is not the current tab.
+		tab_container->add_child(tab1);
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+
+		// Can change current by showing child now after children have been added.
+		// This queues the current tab to update on entering the tree.
+		tab1->show();
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		CHECK(tab0->is_visible());
+		CHECK(tab1->is_visible());
+
+		SceneTree::get_singleton()->get_root()->add_child(tab_container);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 2);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+	}
+
+	SUBCASE("[TabContainer] setting current tab and changing child visibility after adding") {
+		tab_container->add_child(tab0);
+		tab_container->add_child(tab1);
+		tab_container->add_child(tab2);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		tab2->show();
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+		SIGNAL_CHECK_FALSE("tab_selected");
+		SIGNAL_CHECK_FALSE("tab_changed");
+		CHECK(tab0->is_visible());
+		CHECK_FALSE(tab1->is_visible());
+		CHECK(tab2->is_visible());
+
+		// Whichever happens last will have priority.
+		tab_container->set_current_tab(1);
+		CHECK(tab_container->get_current_tab() == 0);
+		CHECK(tab_container->get_previous_tab() == -1);
+
+		// Current tab is set when entering the tree.
+		SceneTree::get_singleton()->get_root()->add_child(tab_container);
+		MessageQueue::get_singleton()->flush();
+		CHECK(tab_container->get_tab_count() == 3);
+		CHECK(tab_container->get_current_tab() == 1);
+		CHECK(tab_container->get_previous_tab() == 0);
+		SIGNAL_CHECK("tab_selected", build_array(build_array(1)));
+		SIGNAL_CHECK("tab_changed", build_array(build_array(1)));
+		CHECK_FALSE(tab0->is_visible());
+		CHECK(tab1->is_visible());
+		CHECK_FALSE(tab2->is_visible());
+	}
+
+	SIGNAL_UNWATCH(tab_container, "tab_selected");
+	SIGNAL_UNWATCH(tab_container, "tab_changed");
+
+	memdelete(tab2);
+	memdelete(tab1);
+	memdelete(tab0);
+	memdelete(tab_container);
+}
+
+TEST_CASE("[SceneTree][TabContainer] layout and offset") {
+	TabContainer *tab_container = memnew(TabContainer);
+	SceneTree::get_singleton()->get_root()->add_child(tab_container);
+	tab_container->set_clip_tabs(false);
+
+	Control *tab0 = memnew(Control);
+	tab0->set_name("tab0");
+	Control *tab1 = memnew(Control);
+	tab1->set_name("tab1 ");
+	Control *tab2 = memnew(Control);
+	tab2->set_name("tab2    ");
+
+	tab_container->add_child(tab0);
+	tab_container->add_child(tab1);
+	tab_container->add_child(tab2);
+
+	MessageQueue::get_singleton()->flush();
+
+	Size2 all_tabs_size = tab_container->get_size();
+	const float side_margin = tab_container->get_theme_constant("side_margin");
+
+	TabBar *tab_bar = tab_container->get_tab_bar();
+
+	Vector<Rect2> tab_rects = {
+		tab_bar->get_tab_rect(0),
+		tab_bar->get_tab_rect(1),
+		tab_bar->get_tab_rect(2)
+	};
+
+	SUBCASE("[TabContainer] tabs are arranged next to each other") {
+		// Horizontal positions are next to each other.
+		CHECK(tab_rects[0].position.x == 0);
+		CHECK(tab_rects[1].position.x == tab_rects[0].size.x);
+		CHECK(tab_rects[2].position.x == tab_rects[1].position.x + tab_rects[1].size.x);
+
+		// Fills the entire width.
+		CHECK(tab_rects[2].position.x + tab_rects[2].size.x == all_tabs_size.x - side_margin);
+
+		// Horizontal sizes are positive.
+		CHECK(tab_rects[0].size.x > 0);
+		CHECK(tab_rects[1].size.x > 0);
+		CHECK(tab_rects[2].size.x > 0);
+
+		// Vertical positions are at 0.
+		CHECK(tab_rects[0].position.y == 0);
+		CHECK(tab_rects[1].position.y == 0);
+		CHECK(tab_rects[2].position.y == 0);
+
+		// Vertical sizes are the same.
+		CHECK(tab_rects[0].size.y == tab_rects[1].size.y);
+		CHECK(tab_rects[1].size.y == tab_rects[2].size.y);
+	}
+
+	SUBCASE("[TabContainer] tab position") {
+		float tab_height = tab_rects[0].size.y;
+		Ref<StyleBox> panel_style = tab_container->get_theme_stylebox("panel_style");
+
+		// Initial position, same as top position.
+		// Tab bar is at the top.
+		CHECK(tab_bar->get_anchor(SIDE_TOP) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_BOTTOM) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab_bar->get_offset(SIDE_TOP) == 0);
+		CHECK(tab_bar->get_offset(SIDE_BOTTOM) == tab_height);
+		CHECK(tab_bar->get_offset(SIDE_LEFT) == side_margin);
+		CHECK(tab_bar->get_offset(SIDE_RIGHT) == 0);
+
+		// Child is expanded and below the tab bar.
+		CHECK(tab0->get_anchor(SIDE_TOP) == 0);
+		CHECK(tab0->get_anchor(SIDE_BOTTOM) == 1);
+		CHECK(tab0->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab0->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab0->get_offset(SIDE_TOP) == tab_height);
+		CHECK(tab0->get_offset(SIDE_BOTTOM) == 0);
+		CHECK(tab0->get_offset(SIDE_LEFT) == 0);
+		CHECK(tab0->get_offset(SIDE_RIGHT) == 0);
+
+		// Bottom position.
+		tab_container->set_tabs_position(TabContainer::POSITION_BOTTOM);
+		CHECK(tab_container->get_tabs_position() == TabContainer::POSITION_BOTTOM);
+		MessageQueue::get_singleton()->flush();
+
+		// Tab bar is at the bottom.
+		CHECK(tab_bar->get_anchor(SIDE_TOP) == 1);
+		CHECK(tab_bar->get_anchor(SIDE_BOTTOM) == 1);
+		CHECK(tab_bar->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab_bar->get_offset(SIDE_TOP) == -tab_height);
+		CHECK(tab_bar->get_offset(SIDE_BOTTOM) == 0);
+		CHECK(tab_bar->get_offset(SIDE_LEFT) == side_margin);
+		CHECK(tab_bar->get_offset(SIDE_RIGHT) == 0);
+
+		// Child is expanded and above the tab bar.
+		CHECK(tab0->get_anchor(SIDE_TOP) == 0);
+		CHECK(tab0->get_anchor(SIDE_BOTTOM) == 1);
+		CHECK(tab0->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab0->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab0->get_offset(SIDE_TOP) == 0);
+		CHECK(tab0->get_offset(SIDE_BOTTOM) == -tab_height);
+		CHECK(tab0->get_offset(SIDE_LEFT) == 0);
+		CHECK(tab0->get_offset(SIDE_RIGHT) == 0);
+
+		// Top position.
+		tab_container->set_tabs_position(TabContainer::POSITION_TOP);
+		CHECK(tab_container->get_tabs_position() == TabContainer::POSITION_TOP);
+		MessageQueue::get_singleton()->flush();
+
+		// Tab bar is at the top.
+		CHECK(tab_bar->get_anchor(SIDE_TOP) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_BOTTOM) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab_bar->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab_bar->get_offset(SIDE_TOP) == 0);
+		CHECK(tab_bar->get_offset(SIDE_BOTTOM) == tab_height);
+		CHECK(tab_bar->get_offset(SIDE_LEFT) == side_margin);
+		CHECK(tab_bar->get_offset(SIDE_RIGHT) == 0);
+
+		// Child is expanded and below the tab bar.
+		CHECK(tab0->get_anchor(SIDE_TOP) == 0);
+		CHECK(tab0->get_anchor(SIDE_BOTTOM) == 1);
+		CHECK(tab0->get_anchor(SIDE_LEFT) == 0);
+		CHECK(tab0->get_anchor(SIDE_RIGHT) == 1);
+		CHECK(tab0->get_offset(SIDE_TOP) == tab_height);
+		CHECK(tab0->get_offset(SIDE_BOTTOM) == 0);
+		CHECK(tab0->get_offset(SIDE_LEFT) == 0);
+		CHECK(tab0->get_offset(SIDE_RIGHT) == 0);
+	}
+
+	memdelete(tab_container);
+}
+
+// FIXME: Add tests for mouse click, keyboard navigation, and drag and drop.
+
+} // namespace TestTabContainer
+
+#endif // TEST_TAB_CONTAINER_H