Add integration tests

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

runtests.sh

@@ -0,0 +1,28 @@
+#!/bin/bash
+function die() {
+    local msg
+    msg="$1"
+    echo "$msg - exiting"
+    exit 1
+}
+
+here="$(realpath "$(dirname "$0")")"
+tests="$here/tests"
+flags="--quiet --release"
+
+echo "building"
+cargo build $flags || die "build failed"
+
+echo "testing"
+find "$tests" -type f -name '*.npp' | while read f; do
+    result="$(cargo run $flags -- "$f")"
+
+    echo "$result" > "$f.got"
+
+    if [[ "$result" != "$(cat "$f.expect")" ]]; then
+        echo "$f did not match expected output"
+        diff "$f.got" "$f.expect"
+    fi
+done
+
+echo "done"