diff --git a/src/pip4a/base.py b/src/pip4a/base.py
index e8cca4b..d25a296 100644
--- a/src/pip4a/base.py
+++ b/src/pip4a/base.py
@@ -32,7 +32,6 @@ def __init__(self: Base, app: App) -> None:
         self.interpreter: Path
         self.site_pkg_path: Path
         self.python_path: Path
-        self._pip_include_test: bool = False
 
     def _set_interpreter(  # noqa: PLR0912
         self: Base,
diff --git a/src/pip4a/cli.py b/src/pip4a/cli.py
index feddbcf..c88eccf 100644
--- a/src/pip4a/cli.py
+++ b/src/pip4a/cli.py
@@ -91,6 +91,7 @@ def ensure_isolated(self: Cli) -> None:
 
     def run(self: Cli) -> None:
         """Run the application."""
+        logger = logging.getLogger("pip4a")
         collection_name, dependencies = get_galaxy()
 
         self.app = App(
@@ -98,6 +99,10 @@ def run(self: Cli) -> None:
             collection_name=collection_name,
             collection_dependencies=dependencies,
         )
+        if "," in self.app.args.collection_specifier:
+            err = "Multiple optional dependencies are not supported at this time."
+            logger.critical(err)
+
         if self.app.args.subcommand == "install":
             installer = Installer(self.app)
             installer.run()
diff --git a/src/pip4a/constants.py b/src/pip4a/constants.py
index 7960e04..0ce81a0 100644
--- a/src/pip4a/constants.py
+++ b/src/pip4a/constants.py
@@ -6,7 +6,6 @@
 class Constants:
     """Constants, for now, for pip4a."""
 
-    TEST_REQUIREMENTS_PY = Path("./test-requirements.txt").resolve()
     WORKING_DIR = Path("./.pip4a_cache").resolve()
     COLLECTION_BUILD_DIR = WORKING_DIR / "src"
     DISCOVERED_PYTHON_REQS = WORKING_DIR / "discovered_requirements.txt"
diff --git a/src/pip4a/installer.py b/src/pip4a/installer.py
index 50fb87e..4c027cd 100644
--- a/src/pip4a/installer.py
+++ b/src/pip4a/installer.py
@@ -12,7 +12,7 @@
 
 from .base import Base
 from .constants import Constants as C  # noqa: N817
-from .utils import oxford_join, subprocess_run
+from .utils import opt_deps_to_files, oxford_join, subprocess_run
 
 
 logger = logging.getLogger(__name__)
@@ -36,9 +36,6 @@ def run(self: Installer) -> None:
         if self.app.args.editable:
             self._swap_editable_collection()
 
-        if "[test]" in self.app.args.collection_specifier:
-            self._pip_include_test = True
-
         self._discover_deps()
         self._pip_install()
         self._check_bindep()
@@ -82,8 +79,10 @@ def _discover_deps(self: Installer) -> None:
             f" --write-bindep {C.DISCOVERED_BINDEP_REQS}"
             " --sanitize"
         )
-        if self._pip_include_test and C.TEST_REQUIREMENTS_PY.exists():
-            command += f" --user-pip {C.TEST_REQUIREMENTS_PY}"
+        opt_deps = re.match(r".*\[(.*)\]", self.app.args.collection_specifier)
+        if opt_deps:
+            for dep in opt_deps_to_files(opt_deps.group(1)):
+                command += f" --user-pip {dep}"
         msg = f"Writing discovered python requirements to: {C.DISCOVERED_PYTHON_REQS}"
         logger.info(msg)
         msg = f"Writing discovered system package requirements to: {C.DISCOVERED_BINDEP_REQS}"
diff --git a/src/pip4a/utils.py b/src/pip4a/utils.py
index e21e657..14380e1 100644
--- a/src/pip4a/utils.py
+++ b/src/pip4a/utils.py
@@ -83,3 +83,29 @@ def oxford_join(words: list[str]) -> str:
     if len(words) == 2:  # noqa: PLR2004
         return " and ".join(words)
     return ", ".join(words[:-1]) + ", and " + words[-1]
+
+
+def opt_deps_to_files(dep_str: str) -> list[Path]:
+    """Convert a string of optional dependencies to a list of files.
+
+    :param dep_str: A string of optional dependencies
+    :return: A list of files
+    """
+    deps = dep_str.split(",")
+    files = []
+    for dep in deps:
+        _dep = dep.strip()
+        variant1 = Path.cwd() / f"{_dep}-requirements.txt"
+        if variant1.exists():
+            files.append(variant1)
+            continue
+        variant2 = Path.cwd() / f"requirements-{_dep}.txt"
+        if variant2.exists():
+            files.append(variant2)
+            continue
+        msg = (
+            f"Failed to find optional dependency file for '{_dep}'."
+            f" Checked for '{variant1.name}' and '{variant2.name}'. Skipping."
+        )
+        logger.warning(msg)
+    return files