[vala/0.48] tests: Add "string concat" test for POSIX to increase coverage

[Rico Tzschichholz <ricotz src gnome org>]

commit d77c840a62251c54d8646898ac8a867d595f311a
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Tue Mar 9 15:52:30 2021 +0100

    tests: Add "string concat" test for POSIX to increase coverage

 tests/Makefile.am              | 1 +
 tests/posix/string-concat.vala | 8 ++++++++
 2 files changed, 9 insertions(+)
---
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 32a265166..34615cd34 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1156,6 +1156,7 @@ LINUX_TESTS += \
        linux/file-commandpipe.vala \
        posix/arrays.vala \
        posix/empty-length-0.vala \
+       posix/string-concat.vala \
        posix/struct_only.vala \
        posix/delegate_only.vala \
        posix/enum_only.vala \
diff --git a/tests/posix/string-concat.vala b/tests/posix/string-concat.vala
new file mode 100644
index 000000000..ead6abeed
--- /dev/null
+++ b/tests/posix/string-concat.vala
@@ -0,0 +1,8 @@
+unowned string get_foo () {
+       return "foo";
+}
+
+void main () {
+       string s = get_foo () + "bar" + "!";
+       assert (s == "foobar!");
+}