Rename TemplateProject -> TestProject & tidy some comments

test/test_projects/base.py

@@ -0,0 +1,39 @@
+import os
+import jinja2
+from typing import Union, Dict, Any
+
+
+FilesDict = Dict[str, Union[str, jinja2.Template]]
+TemplateContext = Dict[str, Any]
+
+
+class TestProject:
+    '''
+    An object that represents a project that can be built by cibuildwheel.
+    Can be manipulated in tests by changing `files` and `template_context`.
+
+    Write out to the filesystem using `generate`.
+    '''
+    files: FilesDict
+    template_context: TemplateContext
+
+    def __init__(self):
+        self.files = {}
+        self.template_context = {}
+
+    def generate(self, path: str):
+        for filename, content in self.files.items():
+            file_path = os.path.join(path, filename)
+            os.makedirs(os.path.dirname(file_path), exist_ok=True)
+
+            with open(file_path, 'w', encoding='utf8') as f:
+                if isinstance(content, jinja2.Template):
+                    content = content.render(self.template_context)
+
+                f.write(content)
+
+    def copy(self):
+        other = TestProject()
+        other.files = self.files.copy()
+        other.template_context = self.template_context.copy()
+        return other