Update test paths after flattening v0 layout

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

v0/buffer.h

@@ -0,0 +1,50 @@
+/**
+ * An interface that wraps files and strings.
+ * Allows stream–like reading from it.
+ */
+#ifndef BUFFER_H
+#define BUFFER_H
+
+/**
+ * An interface to a source of textual data.
+ */
+typedef struct Buffer Buffer;
+
+/**
+ * Opens a file.
+ * 
+ * @param path The path to the file.
+ * @returns The newly–opened buffer.
+ */
+Buffer* buffer_open_file(const char* path);
+
+/**
+ * Opens a string.
+ * 
+ * The string is not copied, and must not be free'd until the
+ * buffer itself has been closed.
+ * 
+ * @param string The contents stored in the buffer.
+ * @returns A newly–opened buffer that reads from the string.
+ */
+Buffer* buffer_open_string(const char* string);
+
+/**
+ * Closes the buffer.
+ * 
+ * @param buffer The buffer to close.
+ */
+void buffer_close(Buffer* buffer);
+
+/**
+ * Reads a single character from the buffer.
+ * 
+ * If there are no more characters in the buffer,
+ * this returns `-1`.
+ * 
+ * @param buffer The buffer to read from.
+ * @returns the next character in the buffer.
+ */
+char buffer_read(Buffer* buffer);
+
+#endif