Travis speed ups

Because the amount of features that the simulator is testing is growing,
the test time is taking a long time. This distributes simulator's tests
over three travis machines to decrease test time.

Add options to defined tests that run one-by-one in a sequential fashion
by defining them in $SINGLE_FEATURES, and allow defining features that
should run together by providing a string of ',' separated list of
multiple tests in $MULTI_FEATURES.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/.travis.yml b/.travis.yml
index 6587e33..54e0bd2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,17 +2,48 @@
 
 language: rust
 
+cache: cargo
+
+matrix:
+  include:
+    # Runs each value defined in $SINGLE_FEATURES by itself in the order
+    # the were defined.
+    - os: linux
+      env: SINGLE_FEATURES="sig-ecdsa enc-kw"
+    - os: linux
+      env: SINGLE_FEATURES="none sig-rsa overwrite-only validate-slot0"
+    - os: linux
+      env: SINGLE_FEATURES="enc-rsa"
+
+    # Values defined in $MULTI_FEATURES consist of any number of features
+    # to be enabled at the same time. The list of multi-values should be
+    # separated by ',' and each list of values is run sequentially in the
+    # defined order.
+    - os: linux
+      env: MULTI_FEATURES="sig-rsa overwrite-only,sig-ecdsa overwrite-only"
+    - os: linux
+      env: MULTI_FEATURES="sig-rsa validate-slot0,sig-ecdsa validate-slot0"
+
+    # FIXME: this test actually fails and must be fixed
+    #- os: linux
+    #  env: MULTI_FEATURES="sig-rsa validate-slot0 overwrite-only"
+
+before_install:
+  - |
+    if [ "$TRAVIS_PULL_REQUEST" != "false" ]; then
+      ./scripts/check-signed-off-by.sh
+      if [ $? -ne 0 ]; then
+        exit 1
+      fi
+    fi
+
+install:
+  - pushd sim
+  - cargo fetch
+  - popd
+
 script:
-  - set -e
-  - if [[ "$TRAVIS_PULL_REQUEST" != "false" ]]; then ./scripts/check-signed-off-by.sh; fi
-  - cd sim
-  - cargo test
-  - cargo test --features sig-rsa
-  - cargo test --features sig-ecdsa
-  - cargo test --features overwrite-only
-  - cargo test --features validate-slot0
-  - cargo test --features enc-rsa
-  - cargo test --features enc-kw
+  - ./scripts/run_tests.sh
 
 notifications:
   slack:
diff --git a/scripts/run_tests.sh b/scripts/run_tests.sh
new file mode 100755
index 0000000..58d1998
--- /dev/null
+++ b/scripts/run_tests.sh
@@ -0,0 +1,48 @@
+#!/bin/bash
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+pushd sim
+
+EXIT_CODE=0
+
+if [[ ! -z $SINGLE_FEATURES ]]; then
+  all_features="sig-rsa sig-ecdsa overwrite-only validate-slot0 enc-rsa enc-kw"
+
+  if [[ $SINGLE_FEATURES =~ "none" ]]; then
+    echo "Running cargo with no features"
+    cargo test
+    rc=$? && [ $rc -ne 0 ] && EXIT_CODE=$rc
+  fi
+
+  for feature in $all_features; do
+    if [[ $SINGLE_FEATURES =~ $feature ]]; then
+      echo "Running cargo for feature=\"${feature}\""
+      cargo test --features $feature
+      rc=$? && [ $rc -ne 0 ] && EXIT_CODE=$rc
+    fi
+  done
+fi
+
+if [[ ! -z $MULTI_FEATURES ]]; then
+  IFS=','
+  read -ra multi_features <<< "$MULTI_FEATURES"
+  for features in "${multi_features[@]}"; do
+    echo "Running cargo for features=\"${features}\""
+    cargo test --features "$features"
+    rc=$? && [ $rc -ne 0 ] && EXIT_CODE=$rc
+  done
+fi
+
+popd
+exit $EXIT_CODE