Add test files.

src/testdir/test90.in

+Tests for sha256() function.    vim: set ft=vim et ts=2 sw=2 :
+
+STARTTEST
+:so small.vim
+:if !has('cryptv') || !exists('*sha256')
+   e! test.ok
+   wq! test.out
+:endif
+:"
+:let testcase='test for empty string: '
+:if sha256("") ==# 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855'
+: let res='ok'
+:else
+: let res='ng'
+:endif
+:$put =testcase.res
+:"
+:let testcase='test for 1 char: '
+:if sha256("a") ==# 'ca978112ca1bbdcafac231b39a23dc4da786eff8147c4e72b9807785afee48bb'
+: let res='ok'
+:else
+: let res='ng'
+:endif
+:$put =testcase.res
+:"
+:let testcase='test for 3 chars: '
+:if sha256("abc") ==# 'ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad'
+: let res='ok'
+:else
+: let res='ng'
+:endif
+:$put =testcase.res
+:"
+:let testcase='test for contains meta char: '
+:if sha256("foo\nbar") ==# '807eff6267f3f926a21d234f7b0cf867a86f47e07a532f15e8cc39ed110ca776'
+: let res='ok'
+:else
+: let res='ng'
+:endif
+:$put =testcase.res
+:"
+:let testcase='test for contains non-ascii char: '
+:if sha256("\xde\xad\xbe\xef") ==# '5f78c33274e43fa9de5659265c1d917e25c03722dcb0b8d27db8d5feaa813953'
+: let res='ok'
+:else
+: let res='ng'
+:endif
+:$put =testcase.res
+"
+:/^start:/,$wq! test.out
+ENDTEST
+
+start:

src/testdir/test90.ok

+start:
+test for empty string: ok
+test for 1 char: ok
+test for 3 chars: ok
+test for contains meta char: ok
+test for contains non-ascii char: ok