add 2nd transformer, simplify usage example factories

q2_dwq2/_examples.py

@@ -10,23 +10,17 @@
 
 import qiime2
 
-from q2_dwq2 import SingleRecordDNAFASTAFormat
-
 
 def seq1_factory():
     seq = skbio.DNA("AACCGGTTGGCCAA", metadata={"id": "seq1"})
-    return _create_seq_artifact(seq)
+    return qiime2.Artifact.import_data(
+        "SingleDNASequence", seq, view_type=skbio.DNA)
 
 
 def seq2_factory():
     seq = skbio.DNA("AACCGCTGGCGAA", metadata={"id": "seq2"})
-    return _create_seq_artifact(seq)
-
-
-def _create_seq_artifact(seq: skbio.DNA):
-    ff = SingleRecordDNAFASTAFormat()
-    seq.write(str(ff.path))
-    return qiime2.Artifact.import_data("SingleDNASequence", ff)
+    return qiime2.Artifact.import_data(
+        "SingleDNASequence", seq, view_type=skbio.DNA)
 
 
 def nw_align_example_1(use):

q2_dwq2/_transformers.py

@@ -19,3 +19,10 @@ def _1(ff: SingleRecordDNAFASTAFormat) -> DNA:
     # by default, DNA.read will read the first sequence in the file
     with ff.open() as fh:
         return DNA.read(fh)
+
+
+@plugin.register_transformer
+def _2(seq: DNA) -> SingleRecordDNAFASTAFormat:
+    ff = SingleRecordDNAFASTAFormat()
+    seq.write(str(ff.path))
+    return ff

q2_dwq2/tests/test_transformers.py

@@ -33,3 +33,22 @@ def test_single_record_fasta_to_DNA_simple2(self):
                        metadata={'id': 'example-sequence-2', 'description': ''})
 
         self.assertEqual(observed, expected)
+
+    def test_DNA_to_single_record_fasta_simple1(self):
+        in_ = DNA('ACCGGTGGAACCGGTAACACCCAC',
+                  metadata={'id': 'example-sequence-1', 'description': ''})
+        tx = self.get_transformer(DNA, SingleRecordDNAFASTAFormat)
+
+        observed = tx(in_)
+        # confirm "round-trip" of DNA -> SingleRecordDNAFASTAFormat -> DNA
+        # results in an observed sequence that is the same as the starting
+        # sequence
+        self.assertEqual(observed.view(DNA), in_)
+
+    def test_DNA_to_single_record_fasta_simple2(self):
+        in_ = DNA('ACCGGTAACCGGTTAACACCCAC',
+                  metadata={'id': 'example-sequence-2', 'description': ''})
+        tx = self.get_transformer(DNA, SingleRecordDNAFASTAFormat)
+
+        observed = tx(in_)
+        self.assertEqual(observed.view(DNA), in_)