### Question:
Base1SubFieldPackager extends ISOBasePackager { protected int getFirstField() { return fld[0] instanceof ISOBitMapPackager ? 1 : 0; }  int unpack(ISOComponent m, byte[] b); @Override byte[] pack(ISOComponent m);  }### Answer:
@Test public void testGetFirstField() throws Throwable { Base1SubFieldPackager base1SubFieldPackager = new Base1SubFieldPackager(); ISOFieldPackager[] fld = new ISOFieldPackager[2]; fld[0] = new X92_BITMAP(100, "testBase1SubFieldPackagerDescription"); base1SubFieldPackager.setFieldPackager(fld); int result = base1SubFieldPackager.getFirstField(); assertEquals(1, result, "result"); }
@Test public void testGetFirstField1() throws Throwable { ISOFieldPackager[] fld = new ISOFieldPackager[1]; Base1SubFieldPackager f126Packager = new Base1Packager.F126Packager(); f126Packager.setFieldPackager(fld); int result = f126Packager.getFirstField(); assertEquals(0, result, "result"); }
@Test public void testGetFirstFieldThrowsNullPointerException() throws Throwable { Base1SubFieldPackager base1SubFieldPackager = new Base1SubFieldPackager(); try { base1SubFieldPackager.getFirstField(); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot load from object array because \"this.fld\" is null", ex.getMessage(), "ex.getMessage()"); } } }