diff --git a/tests/checks/argparse.fish b/tests/checks/argparse.fish
new file mode 100644
index 000000000..4c25a3fbc
--- /dev/null
+++ b/tests/checks/argparse.fish
@@ -0,0 +1,302 @@
+#RUN: %fish %s
+##########
+# Start by verifying a bunch of error conditions.
+
+# No args is an error
+argparse
+#CHECKERR: argparse: No option specs were provided
+
+# Missing -- is an error
+argparse h/help
+#CHECKERR: argparse: Missing -- separator
+
+# Flags but no option specs is an error
+argparse -s -- hello
+#CHECKERR: argparse: No option specs were provided
+
+# Invalid option specs
+argparse h-
+argparse +help
+argparse h/help:
+argparse h-help::
+argparse h-help=x
+#CHECKERR: argparse: Invalid option spec 'h-' at char '-'
+#CHECKERR: argparse: Short flag '+' invalid, must be alphanum or '#'
+#CHECKERR: argparse: Invalid option spec 'h/help:' at char ':'
+#CHECKERR: argparse: Invalid option spec 'h-help::' at char ':'
+#CHECKERR: argparse: Invalid option spec 'h-help=x' at char 'x'
+
+# --max-args and --min-args work
+begin
+    argparse --name min-max --min-args 1 h/help --
+    #CHECKERR: min-max: Expected at least 1 args, got only 0
+    argparse --name min-max --min-args 1 --max-args 3 h/help -- arg1
+    argparse --name min-max --min-args 1 --max-args 3 h/help -- arg1 arg2
+    argparse --name min-max --min-args 1 --max-args 3 h/help -- --help arg1 arg2 arg3
+    argparse --name min-max --min-args 1 --max-args 3 h/help -- arg1 arg2 -h arg3 arg4
+    #CHECKERR: min-max: Expected at most 3 args, got 4
+    argparse --name min-max --max-args 1 h/help --
+    argparse --name min-max --max-args 1 h/help -- arg1
+    argparse --name min-max --max-args 1 h/help -- arg1 arg2
+    #CHECKERR: min-max: Expected at most 1 args, got 2
+end
+
+# Invalid \"#-val\" spec
+begin
+    argparse '#-val=' -- abc -x def
+    # CHECKERR: argparse: Implicit int short flag '#' does not allow modifiers like '='
+end
+
+# Invalid arg in the face of a \"#-val\" spec
+begin
+    argparse '#-val' -- abc -x def
+    # CHECKERR: argparse: Unknown option '-x'
+    # CHECKERR: {{.*}}argparse.fish (line {{\d+}}):
+    # CHECKERR: argparse '#-val' -- abc -x def
+    # CHECKERR: {{\s*\^\s*}}
+end
+
+# Defining a short flag more than once
+begin
+    argparse 's/short' 'x/xray' 's/long' -- -s -x --long
+    # CHECKERR: argparse: Short flag 's' already defined
+end
+
+# Defining a long flag more than once
+begin
+    argparse 's/short' 'x/xray' 'l/short' -- -s -x --long
+    # CHECKERR: argparse: Long flag 'short' already defined
+end
+
+# Defining an implicit int flag more than once
+begin
+    argparse '#-val' 'x/xray' 'v#val' -- -s -x --long
+    # CHECKERR: argparse: Implicit int flag '#' already defined
+end
+
+# Defining an implicit int flag with modifiers
+begin
+    argparse 'v#val=' --
+    # CHECKERR: argparse: Implicit int short flag 'v' does not allow modifiers like '='
+end
+
+##########
+# Now verify that validly formed invocations work as expected.
+
+# No args
+begin
+    argparse h/help --
+end
+
+# One arg and no matching flags
+begin
+    argparse h/help -- help
+    set -l
+    # CHECK: argv help
+end
+
+# Five args with two matching a flag
+begin
+    argparse h/help -- help --help me -h 'a lot more'
+    set -l
+    # CHECK: _flag_h '--help'  '-h'
+    # CHECK: _flag_help '--help'  '-h'
+    # CHECK: argv 'help'  'me'  'a lot more'
+end
+
+# Required, optional, and multiple flags
+begin
+    argparse 'h/help' 'a/abc=' 'd/def=?' 'g/ghk=+' -- help --help me --ghk=g1 --abc=ABC --ghk g2 --d -g g3
+    set -l
+    # CHECK: _flag_a ABC
+    # CHECK: _flag_abc ABC
+    # CHECK: _flag_d
+    # CHECK: _flag_def
+    # CHECK: _flag_g 'g1'  'g2'  'g3'
+    # CHECK: _flag_ghk 'g1'  'g2'  'g3'
+    # CHECK: _flag_h --help
+    # CHECK: _flag_help --help
+    # CHECK: argv 'help'  'me'
+end
+
+# --stop-nonopt works
+begin
+    argparse --stop-nonopt 'h/help' 'a/abc=' -- -a A1 -h --abc A2 non-opt 'second non-opt' --help
+    set -l
+    # CHECK: _flag_a A2
+    # CHECK: _flag_abc A2
+    # CHECK: _flag_h -h
+    # CHECK: _flag_help -h
+    # CHECK: argv 'non-opt'  'second non-opt'  '--help'
+end
+
+# Implicit int flags work
+begin
+    argparse '#-val' -- abc -123 def
+    set -l
+    # CHECK: _flag_val 123
+    # CHECK: argv 'abc'  'def'
+end
+begin
+    argparse 'v/verbose' '#-val' 't/token=' -- -123 a1 --token woohoo --234 -v a2 --verbose
+    set -l
+    # CHECK: _flag_t woohoo
+    # CHECK: _flag_token woohoo
+    # CHECK: _flag_v '-v'  '--verbose'
+    # CHECK: _flag_val -234
+    # CHECK: _flag_verbose '-v'  '--verbose'
+    # CHECK: argv 'a1'  'a2'
+end
+
+# Should be set to 987
+begin
+    argparse 'm#max' -- argle -987 bargle
+    set -l
+    # CHECK: _flag_m 987
+    # CHECK: _flag_max 987
+    # CHECK: argv 'argle'  'bargle'
+end
+
+# Should be set to 765
+begin
+    argparse 'm#max' -- argle -987 bargle --max 765
+    set -l
+    # CHECK: _flag_m 765
+    # CHECK: _flag_max 765
+    # CHECK: argv 'argle'  'bargle'
+end
+
+# Bool short flag only
+begin
+    argparse 'C' 'v' -- -C -v arg1 -v arg2
+    set -l
+    # CHECK: _flag_C -C
+    # CHECK: _flag_v '-v'  '-v'
+    # CHECK: argv 'arg1'  'arg2'
+end
+
+# Value taking short flag only
+begin
+    argparse 'x=' 'v/verbose' -- --verbose arg1 -v -x arg2
+    set -l
+    # CHECK: _flag_v '--verbose'  '-v'
+    # CHECK: _flag_verbose '--verbose'  '-v'
+    # CHECK: _flag_x arg2
+    # CHECK: argv arg1
+end
+
+# Implicit int short flag only
+begin
+    argparse 'x#' 'v/verbose' -- -v -v argle -v -x 321 bargle
+    set -l
+    # CHECK: _flag_v '-v'  '-v'  '-v'
+    # CHECK: _flag_verbose '-v'  '-v'  '-v'
+    # CHECK: _flag_x 321
+    # CHECK: argv 'argle'  'bargle'
+end
+
+# Implicit int short flag only with custom validation passes
+begin
+    argparse 'x#!_validate_int --max 500' 'v/verbose' -- -v -v -x 499 -v
+    set -l
+    # CHECK: _flag_v '-v'  '-v'  '-v'
+    # CHECK: _flag_verbose '-v'  '-v'  '-v'
+    # CHECK: _flag_x 499
+    # CHECK: argv
+end
+
+# Implicit int short flag only with custom validation fails
+begin
+    argparse 'x#!_validate_int --min 500' 'v/verbose' -- -v -v -x 499 -v
+    set -l
+    # CHECKERR: argparse: Value '499' for flag 'x' less than min allowed of '500'
+end
+
+##########
+# Verify that flag value validation works.
+
+# Implicit int flag validation fails
+argparse 'm#max' -- argle --max 765x bargle
+and echo unxpected argparse return status >&2
+argparse 'm#max' -- argle -ma1 bargle
+and echo unxpected argparse return status >&2
+# CHECKERR: argparse: Value '765x' for flag 'max' is not an integer
+# CHECKERR: argparse: Value 'a1' for flag 'm' is not an integer
+
+# Check the exit status from argparse validation
+argparse 'm#max!set | grep _flag_; function x; return 57; end; x' -- argle --max=83 bargle 2>&1
+set -l saved_status $status
+test $saved_status -eq 57
+and echo expected argparse return status $saved_status
+# CHECK: _flag_name max
+# CHECK: _flag_value 83
+# CHECK: expected argparse return status 57
+
+# Explicit int flag validation
+# These should fail
+argparse 'm#max!_validate_int --min 1 --max 1' -- argle -m2 bargle
+and echo unexpected argparse return status $status >&2
+argparse 'm#max!_validate_int --min 0 --max 1' -- argle --max=-1 bargle
+and echo unexpected argparse return status $status >&2
+# CHECKERR: argparse: Value '2' for flag 'm' greater than max allowed of '1'
+# CHECKERR: argparse: Value '-1' for flag 'max' less than min allowed of '0'
+# These should succeed
+argparse 'm/max=!_validate_int --min 0 --max 1' -- argle --max=0 bargle
+or echo unexpected argparse return status $status >&2
+argparse 'm/max=!_validate_int --min 0 --max 1' -- argle --max=1 bargle
+or echo unexpected argparse return status $status >&2
+
+# Errors use function name by default
+function notargparse
+    argparse a/alpha -- --banana
+end
+notargparse
+# CHECKERR: notargparse: Unknown option '--banana'
+# CHECKERR: {{.*}}argparse.fish (line {{\d+}}):
+# CHECKERR:     argparse a/alpha -- --banana
+# CHECKERR:     ^
+# CHECKERR: in function 'notargparse'
+# CHECKERR: called on line {{\d+}} of file {{.*}}argparse.fish
+
+true
+
+# Ignoring unknown options
+argparse -i a=+ b=+ -- -a alpha -b bravo -t tango -a aaaa --wurst
+or echo unexpected argparse return status $status >&2
+# The unknown options are removed _entirely_.
+echo $argv
+echo $_flag_a
+# CHECK: -t tango --wurst
+# CHECK: alpha aaaa
+
+# Check for crash when last option is unknown
+argparse -i b/break -- "-b kubectl get pods -l name=foo"
+
+begin
+    # Checking arguments after "--"
+    argparse a/alpha -- a --alpha -- b -a
+    printf '%s\n' $argv
+    # CHECK: a
+    # CHECK: b
+    # CHECK: -a
+end
+
+# #5864 - short flag only with same validation function.
+# Checking validation for short flags only
+argparse 'i=!_validate_int' 'o=!_validate_int' -- -i 2 -o banana
+argparse 'i=!_validate_int' 'o=!_validate_int' -- -i -o banana
+# CHECKERR: argparse: Value 'banana' for flag 'o' is not an integer
+# CHECKERR: argparse: Value '-o' for flag 'i' is not an integer
+begin
+    argparse 'i=!_validate_int' 'o=!_validate_int' -- -i 2 -o 3
+    set -l
+    # CHECK: _flag_a 'alpha'  'aaaa'
+    # CHECK: _flag_b -b
+    # CHECK: _flag_break -b
+    # CHECK: _flag_i 2
+    # CHECK: _flag_m 1
+    # CHECK: _flag_max 1
+    # CHECK: _flag_o 3
+    # CHECK: argv
+    # CHECK: saved_status 57
+end