signatureFailure("Maven", ['abcd': signatureError(FAILED)])             | 'Artifact was signed with key abcd (not found) but signature didn\'t match'
        signatureFailure("Maven", ['abcd': signatureError(IGNORED_KEY)])        | 'Artifact was signed with an ignored key: abcd (not found)'

     */
    @Test
    public void testSubstringFromLast() throws Exception {
        assertEquals("ab", StringUtil.substringFromLast("abc", "c"));
        assertEquals("abcab", StringUtil.substringFromLast("abcabc", "c"));
        assertEquals("abc", StringUtil.substringFromLast("abc", ""));
        assertEquals("abc", StringUtil.substringFromLast("abc", null));
        assertEquals("abc", StringUtil.substringFromLast("abc", "dddd"));

  }

  public void testConcat_infiniteIterable() throws IOException {
    CharSource source = CharSource.wrap("abcd");
    Iterable<CharSource> cycle = Iterables.cycle(ImmutableList.of(source));
    CharSource concatenated = CharSource.concat(cycle);

    String expected = "abcdabcd";

    // read the first 8 chars manually, since there's no equivalent to ByteSource.slice
    // TODO(cgdecker): Add CharSource.slice?

    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("a")), "abcd");
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("bg")), "bcdgh");
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("ga")), "ghabcd");
  }

  @Test
  public void forTree_depthFirstPreOrder_twoTrees() {

    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("a")), "abcd");
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("bg")), "bcdgh");
    assertEqualCharNodes(traverser.depthFirstPreOrder(charactersOf("ga")), "ghabcd");
  }

  @Test
  public void forTree_depthFirstPreOrder_twoTrees() {

	if err != nil {
		t.Fatal(err)
	}
	// Upload a good object
	_, err = obj.DeleteObject(ctx, bucket, object, ObjectOptions{})
	if err != nil {
		t.Fatal(err)
	}

	// Create "obj" under "bucket".
	_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)

		}
		return out
	})
}

// test tests an arbitrary suffix array construction function.
// Generates many inputs, builds and checks suffix arrays.
func test(t *testing.T, build func([]byte) []int) {
	t.Run("ababab...", func(t *testing.T) {
		// Very repetitive input has numLMS = len(x)/2-1
		// at top level, the largest it can be.
		// But maxID is only two (aba and ab$).
		size := 100000
		if testing.Short() {

				if err != nil {
					t.Errorf("i=%d, firstN=%d, flush=%t: NewWriter: %v", i, firstN, flush, err)
					continue
				}
				for _, n := range tc {
					want = append(want, abcabc[:n]...)
					if _, err := w.Write(abcabc[:n]); err != nil {
						t.Errorf("i=%d, firstN=%d, flush=%t: Write: %v", i, firstN, flush, err)
						continue outer
					}
					if !flush {
						continue
					}

			{
				bad: []string{"ip:2000:abcd::/32"},
			},
		},
		intermediates: [][]constraintsSpec{
			{
				{},
			},
		},
		leaf: leafSpec{
			sans: []string{"ip:2000:abcd::"},
		},
		expectedError: "\"2000:abcd::\" is excluded",
	},

	// #36: IPv6 constraints do not permit IPv4 addresses.
	{
		roots: []constraintsSpec{
			{
				ok: []string{"ip:2000:abcd::/32"},
			},
		},

		{token: "Abcdef.1234567890123456", expectedError: true, bts: nil},  // invalid token id
		{token: "123456.AABBCCDDEEFFGGHH", expectedError: true, bts: nil},  // invalid token secret
		{token: "123456.AABBCCD-EEFFGGHH", expectedError: true, bts: nil},  // invalid character
		{token: "abc*ef.1234567890123456", expectedError: true, bts: nil},  // invalid character