### Question:
Canvas { private static void box(char c, int i) { i = i - PRIVATE; assert boxchars[i] == 0 : "Double usage " + c + " " + i; assert c != 0; boxchars[i] = c; } Canvas(int width, int height); Canvas clear(); Canvas clear(char c); Canvas box(int x, int y, int w, int h); Canvas box(int x, int y, int w, int h, Style style); Canvas line(int x1, int y1, int x2, int y2, int what); Canvas line(int x1, int y1, int x2, int y2, char what); Canvas merge(int x, int y, int what); Canvas merge(int x, int y, char what); char set(int x, int y, char what); char get(int x, int y); int width(); int height(); @Override String toString(); void toString(StringBuilder sb); Canvas box(); Canvas box(Style style); Canvas merge(Canvas secondary, int dx, int dy); void set(int x, int y, String message);  }### Answer:
@Test public void testCanvasBold() { Canvas c = new Canvas(10, 10); c.box(0, 0, 10, 10, Canvas.BOLD); assertEquals( "" + "┏━━━━━━━━┓\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┃ ┃\n" + "┗━━━━━━━━┛\n" + "", c.toString()); c.box(2, 2, 6, 6, Canvas.BOLD); assertEquals("" + "┏━━━━━━━━┓\n" + "┃ ┃\n" + "┃ ┏━━━━┓ ┃\n" + "┃ ┃ ┃ ┃\n" + "┃ ┃ ┃ ┃\n" + "┃ ┃ ┃ ┃\n" + "┃ ┃ ┃ ┃\n" + "┃ ┗━━━━┛ ┃\n" + "┃ ┃\n" + "┗━━━━━━━━┛\n" + "", c.toString()); c.box(0, 0, 6, 6, Canvas.BOLD); assertEquals("" + "┏━━━━┳━━━┓\n" + "┃ ┃ ┃\n" + "┃ ┏━━╋━┓ ┃\n" + "┃ ┃ ┃ ┃ ┃\n" + "┃ ┃ ┃ ┃ ┃\n" + "┣━╋━━┛ ┃ ┃\n" + "┃ ┃ ┃ ┃\n" + "┃ ┗━━━━┛ ┃\n" + "┃ ┃\n" + "┗━━━━━━━━┛\n" + "", c.toString()); c.box(6, 6, 4, 4, Canvas.BOLD); assertEquals("" + "┏━━━━┳━━━┓\n" + "┃ ┃ ┃\n" + "┃ ┏━━╋━┓ ┃\n" + "┃ ┃ ┃ ┃ ┃\n" + "┃ ┃ ┃ ┃ ┃\n" + "┣━╋━━┛ ┃ ┃\n" + "┃ ┃ ┏╋━┫\n" + "┃ ┗━━━╋┛ ┃\n" + "┃ ┃ ┃\n" + "┗━━━━━┻━━┛\n" + "", c.toString()); }