add unit test for basic undo/redo of inserts

test/src/test_Buffer.cc

@@ -139,3 +139,57 @@ TEST(BufferTest, adds_a_newline_after_inserted_character_when_inserting_in_an_em
     EXPECT_EQ(ss("J\n"), b.get_string());
     EXPECT_EQ(C('\n'), **it);
 }
+
+TEST(BufferTest, allows_undo_and_redo_of_inserts)
+{
+    std::string s("abc\ndef\nghi\n");
+    Buffer b((const uint8_t *)&s[0], s.size());
+    auto it = b.add_cursor();
+
+    b.enter_insert_mode();
+    b.insert_code_point(*it, C('1'));
+    b.insert_code_point(*it, C('2'));
+    b.exit_insert_mode();
+    EXPECT_EQ(ss("12abc\ndef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('a'), **it);
+
+    it->go_next_line();
+    it->go_right_in_line(false);
+    b.enter_insert_mode();
+    b.insert_code_point(*it, C('3'));
+    b.exit_insert_mode();
+    EXPECT_EQ(ss("12abc\nd3ef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('e'), **it);
+
+    it->go_end_of_line(true);
+    b.insert_code_point(*it, C('$'));
+    EXPECT_EQ(ss("12abc\nd3ef$\nghi\n"), b.get_string());
+    EXPECT_EQ(C('\n'), **it);
+
+    it->go_start_of_line();
+    EXPECT_EQ(C('d'), **it);
+
+    b.undo();
+    EXPECT_EQ(ss("12abc\nd3ef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+
+    b.undo();
+    EXPECT_EQ(ss("12abc\ndef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+
+    b.undo();
+    EXPECT_EQ(ss("abc\ndef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+
+    b.redo();
+    EXPECT_EQ(ss("12abc\ndef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+
+    b.redo();
+    EXPECT_EQ(ss("12abc\nd3ef\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+
+    b.redo();
+    EXPECT_EQ(ss("12abc\nd3ef$\nghi\n"), b.get_string());
+    EXPECT_EQ(C('d'), **it);
+}