patch 9.0.0196: finding value in list may require a for loop

Problem:    Finding value in list may require a for loop.
Solution:   Add indexof(). (Yegappan Lakshmanan, closes #10903)
diff --git a/src/testdir/test_blob.vim b/src/testdir/test_blob.vim
index ff4186a..46f2d61 100644
--- a/src/testdir/test_blob.vim
+++ b/src/testdir/test_blob.vim
@@ -764,4 +764,30 @@
   call assert_equal(0, x)
 endfunc
 
+" Test for the indexof() function
+func Test_indexof()
+  let b = 0zdeadbeef
+  call assert_equal(0, indexof(b, {i, v -> v == 0xde}))
+  call assert_equal(3, indexof(b, {i, v -> v == 0xef}))
+  call assert_equal(-1, indexof(b, {i, v -> v == 0x1}))
+  call assert_equal(1, indexof(b, "v:val == 0xad"))
+  call assert_equal(-1, indexof(b, "v:val == 0xff"))
+
+  call assert_equal(-1, indexof(0z, "v:val == 0x0"))
+  call assert_equal(-1, indexof(test_null_blob(), "v:val == 0xde"))
+  call assert_equal(-1, indexof(b, test_null_string()))
+  call assert_equal(-1, indexof(b, test_null_function()))
+
+  let b = 0z01020102
+  call assert_equal(1, indexof(b, "v:val == 0x02", #{startidx: 0}))
+  call assert_equal(2, indexof(b, "v:val == 0x01", #{startidx: -2}))
+  call assert_equal(-1, indexof(b, "v:val == 0x01", #{startidx: 5}))
+  call assert_equal(0, indexof(b, "v:val == 0x01", #{startidx: -5}))
+  call assert_equal(0, indexof(b, "v:val == 0x01", test_null_dict()))
+
+  " failure cases
+  call assert_fails('let i = indexof(b, "val == 0xde")', 'E121:')
+  call assert_fails('let i = indexof(b, {})', 'E1256:')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab