Added instruction to build and run the tests

README.md

@@ -14,4 +14,26 @@ For example `One number: {:08}; And another one: {:05.3}` is preprocessed into `
 This is returned as a `std::array<char, N>`, where `N` is automatically evaluated. The only code executed at compile
 time then formats the numbers and writes them into their place in the array.
 
-Disclaimer: The actual formatting code is largely shamelessly stolen from `fmtlib`.
+Disclaimer: The actual formatting code is largely shamelessly stolen from `fmtlib`.
+
+## Building and running the tests
+
+1. Initialize the `googletest` framework submodule
+```bash
+$ git submodule update --init
+```
+
+2. Create the build directory
+```bash
+$ cmake -B build -S .
+```
+
+3. Build the project
+```bash
+$ cmake --build build/
+```
+
+4. Run the tests
+```bash
+$ ctest --test-dir build/
+```