added pytests ripped from sacrebleu

.gitignore

@@ -1 +1,5 @@
 data/
+.coverage
+build
+dist
+__pycache__

pytest.ini

@@ -0,0 +1,2 @@
+[pytest]
+addopts = --cov test -v

sacrebleu.py

@@ -83,8 +83,9 @@
 
 # VERSION HISTORY
 
-- 1.1.4 (in progress)
+- next version
    - added effective order for sentence-level BLEU computation
+   - added unit tests from sockeye
 
 - 1.1.3 (8 November 2017).
    - Factored code a bit to facilitate API:

test/test_bleu.py

@@ -0,0 +1,91 @@
+# Copyright 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You may not
+# use this file except in compliance with the License. A copy of the License
+# is located at
+#
+#     http://aws.amazon.com/apache2.0/
+# 
+# or in the "license" file accompanying this file. This file 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.
+
+import pytest
+import sacrebleu
+from collections import namedtuple
+
+EPSILON = 1e-8
+
+Statistics = namedtuple('Statistics', ['common', 'total'])
+
+test_cases = [(["this is a test", "another test"], ["ref1", "ref2"], 0.003799178428257963),
+              (["this is a test"], ["this is a test"], 1.0),
+              (["this is a fest"], ["this is a test"], 0.223606797749979)]
+
+test_case_offset = [("am I am a character sequence", "I am a symbol string sequence a a", 0.1555722182, 0)]
+
+# statistic structure:
+# - common counts
+# - total counts
+# - hyp_count
+# - ref_count
+
+test_case_statistics = [("am I am a character sequence", "I am a symbol string sequence a a",
+                         Statistics([4, 2, 1, 0], [6, 5, 4, 3]))]
+
+test_case_scoring = [((Statistics([9, 7, 5, 3], [10, 8, 6, 4]), 11, 11), 0.8375922397)]
+
+test_effective_order = [(["test"], ["a test"], 0.3678794411714425),
+                        (["a test"], ["a test"], 1.0),
+                        (["a little test"], ["a test"], 0.03218297948685433)]
+
+
+# testing that right score is returned for null statistics and different offsets
+# format: stat, offset, expected score
+test_case_degenerate_stats = [((Statistics([0, 0, 0, 0], [4, 4, 2, 1]), 0, 1), 0.0, 0.0),
+                              ((Statistics([0, 0, 0, 0], [10, 11, 12, 0]), 14, 10), 0.0, 0.0),
+                              ((Statistics([0, 0, 0, 0], [0, 0, 0, 0]), 0, 0), 0.0, 0.0),
+                              ((Statistics([6, 5, 4, 0], [6, 5, 4, 3]), 6, 6), 0.0, 0.0),
+                              ((Statistics([0, 0, 0, 0], [0, 0, 0, 0]), 0, 0), 0.1, 0.0),
+                              ((Statistics([0, 0, 0, 0], [0, 0, 0, 0]), 1, 5), 0.01, 0.0)]
+
+
+@pytest.mark.parametrize("hypotheses, references, expected_bleu", test_cases)
+def test_bleu(hypotheses, references, expected_bleu):
+    bleu = sacrebleu.raw_corpus_bleu(hypotheses, [references], .01).score / 100
+    assert abs(bleu - expected_bleu) < EPSILON
+
+
+@pytest.mark.parametrize("hypotheses, references, expected_bleu", test_effective_order)
+def test_effective_order(hypotheses, references, expected_bleu):
+    bleu = sacrebleu.raw_corpus_bleu(hypotheses, [references], .01).score / 100
+    assert abs(bleu - expected_bleu) < EPSILON
+
+
+@pytest.mark.parametrize("hypothesis, reference, expected_stat", test_case_statistics)
+def test_statistics(hypothesis, reference, expected_stat):
+    result = sacrebleu.raw_corpus_bleu(hypothesis, reference, .01)
+    stat = Statistics(result.counts, result.totals)
+    assert stat == expected_stat
+
+
+@pytest.mark.parametrize("statistics, expected_score", test_case_scoring)
+def test_scoring(statistics, expected_score):
+    score = sacrebleu.compute_bleu(statistics[0].common, statistics[0].total, statistics[1], statistics[2]).score / 100
+    assert abs(score - expected_score) < EPSILON
+
+
+@pytest.mark.parametrize("hypothesis, reference, expected_with_offset, expected_without_offset",
+                         test_case_offset)
+def test_offset(hypothesis, reference, expected_with_offset, expected_without_offset):
+    score_without_offset = sacrebleu.raw_corpus_bleu(hypothesis, reference, 0.0).score / 100
+    assert abs(expected_without_offset - score_without_offset) < EPSILON
+
+    score_with_offset = sacrebleu.raw_corpus_bleu(hypothesis, reference, 0.1).score / 100
+    assert abs(expected_with_offset - score_with_offset) < EPSILON
+
+@pytest.mark.parametrize("statistics, offset, expected_score", test_case_degenerate_stats)
+def test_degenerate_statistics(statistics, offset, expected_score):
+    score = sacrebleu.compute_bleu(statistics[0].common, statistics[0].total, statistics[1], statistics[2], smooth='floor', smooth_floor=offset).score / 100
+    assert score == expected_score