Refine CLI testing

* Make it data driven and test the whole result againsta  JSON file
* Add new test for a requirements files
* Use regeneration of fixtures with the PYINSP_REGEN_TEST_FIXTURES=yes
  environment variable.

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

tests/data/default-url-expected.json

@@ -0,0 +1,34 @@
+{
+  "headers": {
+    "tool_name": "dad",
+    "tool_homepageurl": "https://github.com/nexB/python-inspector",
+    "tool_version": "0.5.0",
+    "options": [
+      "--specifier zipp==3.8.0",
+      "--index-url https://pypi.org/simple",
+      "--python-version 38",
+      "--operating-system linux",
+      "--json <file>"
+    ],
+    "notice": "Dependency tree generated with python-inspector.\npython-inspector is a free software tool from nexB Inc. and others.\nVisit https://github.com/nexB/scancode-toolkit/ for support and download.",
+    "warnings": [],
+    "errors": []
+  },
+  "requirements": [
+    {
+      "purl": "pkg:pypi/zipp@3.8.0",
+      "extracted_requirement": "zipp==3.8.0",
+      "scope": "install",
+      "is_runtime": true,
+      "is_optional": false,
+      "is_resolved": true,
+      "resolved_package": {}
+    }
+  ],
+  "resolved_dependencies": [
+    {
+      "package": "pkg:pypi/zipp@3.8.0",
+      "dependencies": []
+    }
+  ]
+}

tests/data/pinned-requirements.txt

@@ -0,0 +1,27 @@
+attrs==21.4.0
+beautifulsoup4==4.11.1
+certifi==2022.5.18.1
+charset-normalizer==2.0.12
+click==8.0.4
+colorama==0.4.4
+commoncode==30.2.0
+dparse2==0.6.1
+idna==3.3
+importlib-metadata==4.8.3
+intbitset==3.0.1
+packageurl-python==0.9.9
+packaging==21.3
+pip-requirements-parser==31.2.0
+pkginfo2==30.0.0
+pyparsing==3.0.9
+PyYAML==6.0
+requests==2.27.1
+resolvelib==0.8.1
+saneyaml==0.5.2
+soupsieve==2.3.2.post1
+text-unidecode==1.3
+toml==0.10.2
+typing==3.6.6
+typing_extensions==4.1.1
+urllib3==1.26.9
+zipp==3.6.0