diff --git a/tests/functional/n-window/01-past-present-future.t b/tests/functional/n-window/01-past-present-future.t
new file mode 100644
index 00000000000..183b9343b14
--- /dev/null
+++ b/tests/functional/n-window/01-past-present-future.t
@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#-------------------------------------------------------------------------------
+
+# Test window size using graphql and cylc-show for all tasks.
+
+. "$(dirname "$0")/test_header"
+
+set_test_number 7
+
+install_workflow "${TEST_NAME_BASE}" "${TEST_NAME_BASE}"
+
+TEST_NAME="${TEST_NAME_BASE}-validate"
+run_ok "${TEST_NAME}" cylc validate "${WORKFLOW_NAME}"
+
+# First run: task c shuts the scheduler down then fails.
+TEST_NAME="${TEST_NAME_BASE}-run"
+# 'a => b => c => d => e', 'a' sets window size to 2, 'c' uses cylc show on all.
+workflow_run_ok "${TEST_NAME}" cylc play --no-detach --debug "${WORKFLOW_NAME}"
+
+TEST_NAME="${TEST_NAME_BASE}-show-a.past"
+contains_ok "$WORKFLOW_RUN_DIR/show-a.txt" <<__END__
+state: succeeded
+prerequisites: (None)
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-b.past"
+contains_ok "$WORKFLOW_RUN_DIR/show-b.txt" <<__END__
+state: succeeded
+prerequisites: (n/a for past tasks)
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-c.present"
+contains_ok "${WORKFLOW_RUN_DIR}/show-c.txt" <<__END__
+prerequisites: ('-': not satisfied)
+  + 1/b succeeded
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-d.future"
+contains_ok "${WORKFLOW_RUN_DIR}/show-d.txt" <<__END__
+state: waiting
+prerequisites: ('-': not satisfied)
+  - 1/c succeeded
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-e.future"
+contains_ok "${WORKFLOW_RUN_DIR}/show-e.txt" <<__END__
+state: waiting
+prerequisites: ('-': not satisfied)
+  - 1/d succeeded
+__END__
+
+purge
diff --git a/tests/functional/n-window/01-past-present-future/flow.cylc b/tests/functional/n-window/01-past-present-future/flow.cylc
new file mode 100644
index 00000000000..a032274a41e
--- /dev/null
+++ b/tests/functional/n-window/01-past-present-future/flow.cylc
@@ -0,0 +1,41 @@
+[scheduler]
+   allow implicit tasks = True
+   [[events]]
+      inactivity timeout = PT1M
+      abort on inactivity timeout = True
+[scheduling]
+   [[graph]]
+      R1 = """
+         a => b => c => d => e
+      """
+[runtime]
+   [[a]]
+      script = """
+set +e
+
+read -r -d '' gqlDoc <<_DOC_
+{"request_string": "
+mutation {
+  setGraphWindowExtent (
+    workflows: [\"${CYLC_WORKFLOW_ID}\"],
+    nEdgeDistance: 2) {
+    result
+  }
+}",
+"variables": null}
+_DOC_
+
+echo "${gqlDoc}"
+
+cylc client "$CYLC_WORKFLOW_ID" graphql < <(echo ${gqlDoc}) 2>/dev/null
+
+set -e
+"""
+   [[c]]
+      script = """
+cylc show "$CYLC_WORKFLOW_ID//1/a" >> $CYLC_WORKFLOW_RUN_DIR/show-a.txt
+cylc show "$CYLC_WORKFLOW_ID//1/b" >> $CYLC_WORKFLOW_RUN_DIR/show-b.txt
+cylc show "$CYLC_WORKFLOW_ID//1/c" >> $CYLC_WORKFLOW_RUN_DIR/show-c.txt
+cylc show "$CYLC_WORKFLOW_ID//1/d" >> $CYLC_WORKFLOW_RUN_DIR/show-d.txt
+cylc show "$CYLC_WORKFLOW_ID//1/e" >> $CYLC_WORKFLOW_RUN_DIR/show-e.txt
+"""
diff --git a/tests/functional/n-window/02-big-window.t b/tests/functional/n-window/02-big-window.t
new file mode 100644
index 00000000000..2dc41f239a1
--- /dev/null
+++ b/tests/functional/n-window/02-big-window.t
@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#-------------------------------------------------------------------------------
+
+# Test large window size using graphql and find tasks in window.
+# This is helpful with coverage by using most the no-rewalk mechanics.
+
+. "$(dirname "$0")/test_header"
+
+set_test_number 5
+
+install_workflow "${TEST_NAME_BASE}" "${TEST_NAME_BASE}"
+
+TEST_NAME="${TEST_NAME_BASE}-validate"
+run_ok "${TEST_NAME}" cylc validate "${WORKFLOW_NAME}"
+
+# First run: task c shuts the scheduler down then fails.
+TEST_NAME="${TEST_NAME_BASE}-run"
+# 'a => b => . . . f => g => h', 'a' sets window size to 5,
+# 'b => i => j => f', 'c' finds 'a', 'j', 'h'
+workflow_run_ok "${TEST_NAME}" cylc play --no-detach --debug "${WORKFLOW_NAME}"
+
+TEST_NAME="${TEST_NAME_BASE}-show-a.past"
+contains_ok "$WORKFLOW_RUN_DIR/show-a.txt" <<__END__
+state: succeeded
+prerequisites: (None)
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-j.parallel"
+contains_ok "${WORKFLOW_RUN_DIR}/show-j.txt" <<__END__
+state: waiting
+prerequisites: ('-': not satisfied)
+  - 1/i succeeded
+__END__
+
+TEST_NAME="${TEST_NAME_BASE}-show-h.future"
+contains_ok "${WORKFLOW_RUN_DIR}/show-h.txt" <<__END__
+state: waiting
+prerequisites: ('-': not satisfied)
+  - 1/g succeeded
+__END__
+
+purge
diff --git a/tests/functional/n-window/02-big-window/flow.cylc b/tests/functional/n-window/02-big-window/flow.cylc
new file mode 100644
index 00000000000..09e4d8181fc
--- /dev/null
+++ b/tests/functional/n-window/02-big-window/flow.cylc
@@ -0,0 +1,52 @@
+[scheduler]
+   allow implicit tasks = True
+   [[events]]
+      inactivity timeout = PT1M
+      abort on inactivity timeout = True
+[scheduling]
+   [[graph]]
+      R1 = """
+         a => b => c => d => e => f => g => h
+         b => i => j => f
+      """
+[runtime]
+   [[a]]
+      script = """
+set +e
+
+read -r -d '' gqlDoc <<_DOC_
+{"request_string": "
+mutation {
+  setGraphWindowExtent (
+    workflows: [\"${CYLC_WORKFLOW_ID}\"],
+    nEdgeDistance: 5) {
+    result
+  }
+}",
+"variables": null}
+_DOC_
+
+echo "${gqlDoc}"
+
+cylc client "$CYLC_WORKFLOW_ID" graphql < <(echo ${gqlDoc}) 2>/dev/null
+
+set -e
+"""
+   [[c]]
+      script = """
+cylc show "$CYLC_WORKFLOW_ID//1/a" >> $CYLC_WORKFLOW_RUN_DIR/show-a.txt
+cylc show "$CYLC_WORKFLOW_ID//1/j" >> $CYLC_WORKFLOW_RUN_DIR/show-j.txt
+cylc show "$CYLC_WORKFLOW_ID//1/h" >> $CYLC_WORKFLOW_RUN_DIR/show-h.txt
+"""
+
+   [[i]]
+      script = """
+# Slow 2nd branch down
+sleep 5
+"""
+
+   [[f]]
+      script = """
+# test re-trigger of old point
+cylc trigger "$CYLC_WORKFLOW_ID//1/b"
+"""
diff --git a/tests/functional/n-window/test_header b/tests/functional/n-window/test_header
new file mode 120000
index 00000000000..90bd5a36f92
--- /dev/null
+++ b/tests/functional/n-window/test_header
@@ -0,0 +1 @@
+../lib/bash/test_header
\ No newline at end of file