Add a test for unexpected warnings

.github/workflows/ci.yml

@@ -12,6 +12,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - name: install test dependencies
+        run: sudo apt-get install libtest-warnings-perl
       - name: autogen
         run: ./autogen
       - name: configure
@@ -24,6 +26,8 @@ jobs:
     runs-on: ubuntu-16.04
     steps:
       - uses: actions/checkout@v2
+      - name: install test dependencies
+        run: sudo apt-get install libtest-warnings-perl
       - name: autogen
         run: ./autogen
       - name: configure

CONTRIBUTING.md

@@ -63,6 +63,7 @@ To add a new test script:
      use Test::More;
      # Your test dependencies go here.
 
+     SKIP: { eval { require Test::Warnings; } or skip($@, 1); }
      eval { require 'ddclient'; } or BAIL_OUT($@);
 
      # Your tests go here.

configure.ac

@@ -27,8 +27,10 @@ m4_foreach_w([_m], [
   ], [AX_PROG_PERL_MODULES([_m], [],
          [AC_MSG_ERROR([missing required Perl module _m])])])
 
-# Perl modules required for tests. Only prints a warning.
+# Perl modules required for tests. Only prints a warning if not
+# installed.
 m4_foreach_w([_m], [
+    Test::Warnings
   ], [AX_PROG_PERL_MODULES([_m], [],
          [AC_MSG_WARN([some tests may be skipped due to missing module _m])])])
 

t/version.pl.in

@@ -1,6 +1,7 @@
 use Test::More;
 use version;
 
+SKIP: { eval { require Test::Warnings; } or skip($@, 1); }
 eval { require 'ddclient'; } or BAIL_OUT($@);
 
 is(ddclient->VERSION(), version->parse('v@PACKAGE_VERSION@'), "version matches Autoconf config");