diff --git a/tests/02-core/03-arg-processor/91-unknown-declaration-opts/expect.md b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/expect.md
new file mode 100644
index 0000000..ed86302
--- /dev/null
+++ b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/expect.md
@@ -0,0 +1,19 @@
+## test
+
+### stderr
+```
+the-cmd: 
+the-cmd:18: Unknown option: --florp
+the-cmd:19: Unknown option: --fleep
+the-cmd:20: Unknown option: --flomp
+the-cmd:21: Unknown option: --beep
+the-cmd:22: Unknown option: --what-the-muffin
+the-cmd:25: Invalid option syntax: -zonk
+the-cmd:26: Invalid option syntax: ---zonk
+the-cmd:27: Invalid option syntax: --Zomg
+Cannot process arguments, due to declaration errors.
+
+the-cmd -- test command
+```
+
+### exit: 1
diff --git a/tests/02-core/03-arg-processor/91-unknown-declaration-opts/info.txt b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/info.txt
new file mode 100644
index 0000000..63b6ed9
--- /dev/null
+++ b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/info.txt
@@ -0,0 +1 @@
+Test for error detection of totally unknown argument declaration options.
diff --git a/tests/02-core/03-arg-processor/91-unknown-declaration-opts/run b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/run
new file mode 100755
index 0000000..2144004
--- /dev/null
+++ b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/run
@@ -0,0 +1,10 @@
+#!/bin/bash
+# Copyright 2022-2023 the Bashy-lib Authors (Dan Bornstein et alia).
+# SPDX-License-Identifier: Apache-2.0
+
+[[ "$(readlink -f "$0")" =~ ^(.*/tests/) ]] && . "${BASH_REMATCH[1]}_test-init.sh" || exit 1
+
+cmd="$(this-cmd-dir)/the-cmd"
+
+call-and-log-as-test 'test' \
+    "${cmd}"
diff --git a/tests/02-core/03-arg-processor/91-unknown-declaration-opts/the-cmd b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/the-cmd
new file mode 100755
index 0000000..30346c3
--- /dev/null
+++ b/tests/02-core/03-arg-processor/91-unknown-declaration-opts/the-cmd
@@ -0,0 +1,31 @@
+#!/bin/bash
+# Copyright 2022-2023 the Bashy-lib Authors (Dan Bornstein et alia).
+# SPDX-License-Identifier: Apache-2.0
+
+[[ "$(readlink -f "$0")" =~ ^(.*/tests/) ]] && . "${BASH_REMATCH[1]}_init.sh" || exit 1
+
+
+#
+# Argument parsing
+#
+
+define-usage $'
+    ${name} -- test command
+
+    This is a test command.
+'
+
+opt-value --florp --var=var1 some-value
+opt-choice --fleep=zonk --call=func1 yes no
+opt-toggle --init=23 --flomp --var=var2 boop
+positional-arg --beep=boop --required --var=var3 some-position
+rest-arg --filter='/./' --call=func2 --what-the-muffin the-rest
+
+# Examples of "option-like" but not syntactically correct as options.
+opt-value -zonk --var=v x
+opt-value ---zonk --var=v x
+opt-value --Zomg --var=v x
+
+process-args "$@" || usage --short
+
+echo 'Nopers.'
diff --git a/tests/02-core/03-arg-processor/92-call-or-var/expect.md b/tests/02-core/03-arg-processor/92-call-or-var/expect.md
new file mode 100644
index 0000000..466fcfe
--- /dev/null
+++ b/tests/02-core/03-arg-processor/92-call-or-var/expect.md
@@ -0,0 +1,15 @@
+## test
+
+### stderr
+```
+the-cmd: 
+the-cmd:18: Unknown option: --florp
+the-cmd:19: Unknown option: --fleep
+the-cmd:20: Unknown option: --flomp
+the-cmd:21: Unknown option: --beep
+Cannot process arguments, due to declaration errors.
+
+the-cmd -- test command
+```
+
+### exit: 1
diff --git a/tests/02-core/03-arg-processor/92-call-or-var/info.txt b/tests/02-core/03-arg-processor/92-call-or-var/info.txt
new file mode 100644
index 0000000..224b725
--- /dev/null
+++ b/tests/02-core/03-arg-processor/92-call-or-var/info.txt
@@ -0,0 +1,2 @@
+Test for error detection of the requirement to declare at least
+one of `--call` or `--var`.
diff --git a/tests/02-core/03-arg-processor/92-call-or-var/run b/tests/02-core/03-arg-processor/92-call-or-var/run
new file mode 100755
index 0000000..2144004
--- /dev/null
+++ b/tests/02-core/03-arg-processor/92-call-or-var/run
@@ -0,0 +1,10 @@
+#!/bin/bash
+# Copyright 2022-2023 the Bashy-lib Authors (Dan Bornstein et alia).
+# SPDX-License-Identifier: Apache-2.0
+
+[[ "$(readlink -f "$0")" =~ ^(.*/tests/) ]] && . "${BASH_REMATCH[1]}_test-init.sh" || exit 1
+
+cmd="$(this-cmd-dir)/the-cmd"
+
+call-and-log-as-test 'test' \
+    "${cmd}"
diff --git a/tests/02-core/03-arg-processor/92-call-or-var/the-cmd b/tests/02-core/03-arg-processor/92-call-or-var/the-cmd
new file mode 100755
index 0000000..c0639c8
--- /dev/null
+++ b/tests/02-core/03-arg-processor/92-call-or-var/the-cmd
@@ -0,0 +1,26 @@
+#!/bin/bash
+# Copyright 2022-2023 the Bashy-lib Authors (Dan Bornstein et alia).
+# SPDX-License-Identifier: Apache-2.0
+
+[[ "$(readlink -f "$0")" =~ ^(.*/tests/) ]] && . "${BASH_REMATCH[1]}_init.sh" || exit 1
+
+
+#
+# Argument parsing
+#
+
+define-usage $'
+    ${name} -- test command
+
+    This is a test command.
+'
+
+opt-value some-value
+opt-choice yes no
+opt-toggle boop
+positional-arg --filter='/boop/' some-position
+rest-arg --required the-rest
+
+process-args "$@" || usage --short
+
+echo 'Nopers.'