diff --git a/DEVELOPER.md b/DEVELOPER.md
index 976623e3a6b..15f1e502da1 100644
--- a/DEVELOPER.md
+++ b/DEVELOPER.md
@@ -362,6 +362,8 @@ pytest -v -n auto
 Markers can be used to select subsets of tests. Markers provided in `pytest.ini` include:
 
 - `slow`: tests that take longer than a few seconds to complete
+- `repo`: tests that require external model repositories
+- `large`: tests using large models (from the `modflow6-examples` and `modflow6-largetestmodels` repos)
 - `regression`: tests comparing results from multiple versions
 
 Markers can be used with the `-m <marker>` option, and can be applied in boolean combinations with `and`, `or` and `not`. For instance, to run fast tests in parallel, excluding regression tests:
@@ -386,18 +388,24 @@ Tests using models from external repositories can be selected with the `repo` ma
 pytest -v -n auto -m "repo"
 ```
 
-The test scripts can also be run independently:
+The `large` marker is a subset of the `repo` marker. To test models excluded from commit-triggered CI and only run on GitHub Actions nightly:
 
 ```shell
-# Run MODFLOW 6 test models
+pytest -v -n auto -m "large"
+```
+
+Test scripts for external model repositories can also be run independently:
+
+```shell
+# MODFLOW 6 test models
 pytest -v -n auto test_z01_testmodels_mf6.py
 
-# Run MODFLOW 5 to 6 conversion test models
+# MODFLOW 5 to 6 conversion test models
 pytest -v -n auto test_z02_testmodels_mf5to6.py
 
-# Run example models
+# models from modflow6-examples repo
 pytest -v -n auto test_z03_examples.py
 
-# Run large test models
+# models from modflow6-largetestmodels repo
 pytest -v -n auto test_z03_largetestmodels.py
 ```
diff --git a/autotest/pytest.ini b/autotest/pytest.ini
index 30cd6949ec3..013c63a54ff 100644
--- a/autotest/pytest.ini
+++ b/autotest/pytest.ini
@@ -10,7 +10,7 @@ markers =
     developmode: tests that should only run with IDEVELOPMODE = 1
     gwf: tests for groundwater flow models
     gwt: tests for groundwater transport models
-    ats: tests for adaptive time step utility plugin
-    aux: tests for auxiliary variables plugin
-    lak: tests for flow lake plugin
-    maw: tests for multi-aquifer well plugin
+    ats: tests for adaptive time step package
+    aux: tests for auxiliary variables
+    lak: tests for lake package
+    maw: tests for multi-aquifer well package
diff --git a/autotest/targets.py b/autotest/targets.py
deleted file mode 100644
index e2c9ff54075..00000000000
--- a/autotest/targets.py
+++ /dev/null
@@ -1,98 +0,0 @@
-import os
-import subprocess
-import sys
-
-import flopy
-
-
-def target_pth(target, pth):
-    exe_exists = flopy.which(target, path=pth)
-    # if target does not exist in specified path determine if it
-    # exists anywhere in the path
-    if exe_exists is None:
-        exe_exists = flopy.which(target)
-    if exe_exists is None:
-        exe_exists = os.path.abspath(os.path.join(pth, target))
-        raise Exception(f"{exe_exists} does not exist or is not executable.")
-    return os.path.abspath(exe_exists)
-
-
-target_ext = ""
-target_so = ".so"
-sysinfo = sys.platform.lower()
-if sysinfo.lower() == "win32":
-    target_ext = ".exe"
-    target_so = ".dll"
-elif sysinfo.lower() == "darwin":
-    target_so = ".dylib"
-
-# paths to executables for  previous versions of MODFLOW
-downloaded_bindir = os.path.join("..", "bin", "downloaded")
-rebuilt_bindir = os.path.join("..", "bin", "rebuilt")
-
-# paths to MODFLOW 6 executable, source files, and example files
-bindir = os.path.join("..", "bin")
-
-# create dictionary of valid executable targets for regression tests
-target_dict = {}
-
-target = target_pth(f"mf2005dbl{target_ext}", downloaded_bindir)
-target_dict["mf2005"] = target
-target = target_pth(f"mfnwtdbl{target_ext}", downloaded_bindir)
-target_dict["mfnwt"] = target
-target = target_pth(f"mfusgdbl{target_ext}", downloaded_bindir)
-target_dict["mfusg"] = target
-target = target_pth(f"mflgrdbl{target_ext}", downloaded_bindir)
-target_dict["mflgr"] = target
-target = target_pth(f"mf2005{target_ext}", downloaded_bindir)
-target_dict["mf2005s"] = target
-target = target_pth(f"mt3dms{target_ext}", downloaded_bindir)
-target_dict["mt3dms"] = target
-target = target_pth(f"mf6{target_ext}", rebuilt_bindir)
-target_dict["mf6_regression"] = target
-
-# create MODFLOW 6 target name and add to dictionary
-program = f"mf6{target_ext}"
-target = os.path.join(bindir, program)
-target_dict["mf6"] = target
-
-# create MODFLOW 6 so/dll target name
-tprog = f"libmf6{target_so}"
-ttarg = os.path.join(bindir, tprog)
-target_dict["libmf6"] = ttarg
-
-# add MODFLOW 5 to 6 converter to dictionary of valid executable targets
-tprog = f"mf5to6{target_ext}"
-ttarg = os.path.join(bindir, tprog)
-target_dict["mf5to6"] = ttarg
-
-# add Zonebudget for 6 to dictionary of valid executable targets
-tprog = f"zbud6{target_ext}"
-ttarg = os.path.join(bindir, tprog)
-target_dict["zbud6"] = ttarg
-
-
-def run_exe(argv, ws="."):
-    buff = []
-    proc = subprocess.Popen(
-        argv, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=ws
-    )
-    result, error = proc.communicate()
-    if result is not None:
-        c = result.decode("utf-8")
-        c = c.rstrip("\r\n")
-        print(f"{c}")
-        buff.append(c)
-
-    return proc.returncode, buff
-
-
-def get_mf6_version(version="mf6"):
-    """Function to get MODFLOW 6 version number"""
-    exe = target_dict[version]
-    return_code, buff = run_exe((exe, "-v"))
-    if return_code == 0:
-        version = buff[0].split()[1]
-    else:
-        version = None
-    return version