datacite: add conversion fixtures

The `test_datacite_conversions` function will compare an input
(datacite) document to an expected output (release entity as JSON). This
way, it should not be too hard to add more cases by adding: input,
output - and by increasing the counter in the range loop within the
test.

To view input and result side by side with vim, change into the test
directory and run:

    tests/files/datacite $ ./caseview.sh 18

1 files changed, 17 insertions, 0 deletions

diff --git a/python/tests/files/datacite/caseview.sh b/python/tests/files/datacite/caseview.sh
new file mode 100755
index 00000000..d1e98c04
--- /dev/null
+++ b/python/tests/files/datacite/caseview.sh
@@ -0,0 +1,17 @@
+#!/bin/bash
+#
+# Open input and output in vertical vim split.
+#
+# $ caseview 13
+#
+view() {
+    if [ -z "$1" ]; then
+        echo usage: "$0" CASE-NUMBER
+        exit 1
+    else
+        padded=$(printf "%02d\n" "$1")
+        vim -O "datacite_doc_$padded.json" "datacite_result_$padded.json"
+    fi
+}
+
+view "$@"