Remove tests data v3bw file and refactor test

reading from the file created in the same test

tests/unit/lib/data/v3bw/20180425_131057.v3bw

-1523974147
-version=1.1.0
-earliest_bandwidth=2018-04-16T14:09:07
-file_created=2018-04-25T13:10:57
-generator_started=2018-04-16T14:09:05
-latest_bandwidth=2018-04-17T14:09:07
-software=sbws
-software_version=0.6.1-dev
-====
-bw=54 error_circ=0 error_misc=0 error_stream=1 master_key_ed25519=g+Shk00y9Md0hg1S6ptnuc/wWKbADBgdjT0Kg+TSF3s nick=A node_id=$AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA rtt=456 success=1 time=2018-04-17T14:09:07

tests/unit/lib/test_v3bwfile.py

@@ -112,20 +112,6 @@ def test_v3bwline_from_results_file(datadir):
     assert bwl_str == str(bwl)
 
 
-def test_v3bwfile(datadir, tmpdir):
-    """Test generate v3bw file (including relay_lines)."""
-    # at some point this should be obtained from conftest
-    v3bw = datadir.read('v3bw/20180425_131057.v3bw')
-    results = load_result_file(str(datadir.join("results.txt")))
-    header = V3BWHeader(timestamp_l,
-                        file_created=file_created,
-                        generator_started=generator_started,
-                        earliest_bandwidth=earliest_bandwidth)
-    bwls = [V3BWLine.from_results(results[fp]) for fp in results]
-    f = V3BWFile(header, bwls)
-    assert v3bw == str(f)
-
-
 def test_from_arg_results(datadir, tmpdir, conf, args):
     results = load_result_file(str(datadir.join("results.txt")))
     expected_header = V3BWHeader(timestamp_l,
@@ -136,7 +122,6 @@ def test_from_arg_results(datadir, tmpdir, conf, args):
     v3bwfile = V3BWFile.from_arg_results(args, conf, results)
     assert str(expected_f)[1:] == str(v3bwfile)[1:]
     output = os.path.join(args.output, now_fname())
-    print(output)
     v3bwfile.write(output)
 
 
@@ -146,3 +131,13 @@ def test_from_arg_results_write(datadir, tmpdir, conf, args):
     output = os.path.join(args.output, now_fname())
     v3bwfile.write(output)
     assert os.path.isfile(output)
+
+
+def test_from_arg_results_write_read(datadir, tmpdir, conf, args):
+    results = load_result_file(str(datadir.join("results.txt")))
+    v3bwfile = V3BWFile.from_arg_results(args, conf, results)
+    output = os.path.join(args.output, now_fname())
+    v3bwfile.write(output)
+    with open(output) as fd:
+        v3bw = fd.read()
+    assert v3bw == str(v3bwfile)