Run TravisCI tests on macOS and check for Suggests

.travis.yml

@@ -2,18 +2,39 @@
 
 language: c
 
-sudo: required
-
-dist: trusty
+matrix:
+  include:
+    - name: "Linux tests"
+      os: linux
+      dist: trusty
+      sudo: required
+
+    - name: "macOS tests"
+      os: osx
+      osx_image: xcode8
+
+    - name: "Linux tests conditional Suggests"
+      os: linux
+      dist: trusty
+      sudo: required
+      env: _R_CHECK_DEPENDS_ONLY_=true
 
 before_install:
   - curl -OLs https://eddelbuettel.github.io/r-travis/run.sh && chmod 0755 run.sh
   # add our launchpad repo which has (inter alia) the newest QuantLib
-  - sudo add-apt-repository -y ppa:edd/misc
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+      sudo add-apt-repository -y ppa:edd/misc;
+    fi
   - ./run.sh bootstrap
 
 install:
-  - ./run.sh install_aptget r-cran-runit r-cran-zoo r-cran-timedate r-cran-timeseries r-cran-tseries r-cran-chron r-cran-fts r-cran-tis
+  - |
+    if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then
+      ./run.sh install_aptget r-cran-runit r-cran-zoo r-cran-timedate \
+        r-cran-timeseries r-cran-tseries r-cran-chron r-cran-fts r-cran-tis;
+    elif [[ "$TRAVIS_OS_NAME" == "osx" ]]; then
+      ./run.sh install_r RUnit zoo timeDate timeSeries tseries chron fts tis;
+    fi
 
 script:
   - ./run.sh run_tests