Add test for _list with empty file; fix code

2 files changed, 37 insertions, 6 deletions

diff --git a/yarns/020-metadata-manipulation.yarn b/yarns/020-metadata-manipulation.yarn
index c7616f6..38703bc 100644
--- a/yarns/020-metadata-manipulation.yarn
+++ b/yarns/020-metadata-manipulation.yarn
@@ -16,3 +16,9 @@ metadata file doesn't exist.
     THEN attempt failed
     AND error message matches R465BCX
 
+An empty file should result in empty output.
+
+    GIVEN file METADATA containing ""
+    WHEN user attempts to run distix _list METADATA
+    THEN attempt succeeded
+    AND output is ""
diff --git a/yarns/900-implements.yarn b/yarns/900-implements.yarn
index 4761005..21a9fc9 100644
--- a/yarns/900-implements.yarn
+++ b/yarns/900-implements.yarn
@@ -15,21 +15,37 @@ allow the step to provide the command line arguments, but then also
 adds in options and things to make distix be isolated from, say,
 global configuration etc.
 
+Note that we change the working directory to `$DATADIR` so that any
+filename arguments the step gives refer to files there rather than in
+`$SRCDIR`, which is the default working directory for step execution.
+
     IMPLEMENTS WHEN user attempts to run distix (.*)
-    rm -f "$DATADIR/attempt.exit"
-    rm -f "$DATADIR/attempt.stdout"
-    rm -f "$DATADIR/attempt.stderr"
+    cd "$DATADIR"
+    rm -f attempt.exit attempt.stdout attempt.stderr
     if "$SRCDIR/distix" --no-default-config $MATCH_1 \
-        > "$DATADIR/attempt.stdout" 2> "$DATADIR/attempt.stderr"
+        > attempt.stdout 2> $DATADIR/attempt.stderr
     then
-        echo 0 > "$DATADIR/attempt.exit"
+        echo 0 > attempt.exit
     else
-        echo "$?" > "$DATADIR/attempt.exit"
+        echo "$?" > attempt.exit
     fi
 
 We also need steps for inspecting the results of attempting to run
 distix.
 
+    IMPLEMENTS THEN attempt succeeded
+    cat "$DATADIR/attempt.exit"
+    if ! grep -Fx 0 "$DATADIR/attempt.exit"
+    then
+        echo "Attempt should have succeeded, but didn't" 1>&2
+        exit 1
+    fi
+
+    IMPLEMENTS THEN output is "(.*)"
+    cat "$DATADIR/attempt.stdout"
+    printf "$MATCH_1" > "$DATADIR/temp-stdout"
+    diff -u "$DATADIR/temp-stdout" "$DATADIR/attempt.stdout"
+
     IMPLEMENTS THEN attempt failed
     cat "$DATADIR/attempt.exit" # helps debugging scenarios
     if grep -Fx 0 "$DATADIR/attempt.exit"
@@ -41,3 +57,12 @@ distix.
     IMPLEMENTS THEN error message matches (.*)
     cat "$DATADIR/attempt.stderr"
     grep -e "$MATCH_1" "$DATADIR/attempt.stderr"
+
+File creation
+-------------
+
+We need to provide a way for scenarios to create files with known
+content.
+
+    IMPLEMENTS GIVEN file (\S+) containing "(.*)"
+    printf "$MATCH_2" > "$DATADIR/$MATCH_1"