tests: test some refresh cases

tests/lib/snaps/test-snap-component-refreshes/one

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+hello, from component one (version 1.2)

tests/lib/snaps/test-snap-component-refreshes/snapcraft.yaml

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+name: test-snap-component-refreshes
+summary: A snap with components
+description: |
+  A snap with components used for testing snapd. Uploaded under the
+  [email protected] account.
+version: 1.2
+grade: stable
+confinement: strict
+base: core24
+components:
+  one:
+    summary: Component 1
+    description: First component for test-snap-component-refreshes
+    version: 1.2
+    type: test
+apps:
+  test-snap-component-refreshes:
+    command: test
+parts:
+  copy:
+    plugin: dump
+    source: .
+    organize:
+      one: (component/one)/hello

tests/lib/snaps/test-snap-component-refreshes/test

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+#!/bin/sh -e
+
+if [ $# -ne 1 ]; then
+    echo "pass in a component name to check if it is installed"
+    exit 1
+fi
+
+if [ ! -f "/snap/${SNAP_NAME}/components/${SNAP_REVISION}/${1}/meta/component.yaml" ]; then
+    echo "component ${1} is not installed!"
+    exit 1
+fi
+
+comp_rev=$(basename $(readlink -f "/snap/${SNAP_NAME}/components/${SNAP_REVISION}/${1}"))
+
+echo "component ${1} is installed at revision ${comp_rev}"

tests/main/component-refresh/task.yaml

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+summary: Test refreshing a component from the store
+
+details: |
+  Verifies that we can install a snap and components from the store, refresh the
+  snap+components, and revert the snap+components.
+
+systems: [ubuntu-16.04-64, ubuntu-18.04-64, ubuntu-2*, ubuntu-core-*, fedora-*]
+
+restore: |
+  snap refresh --unhold
+  snap remove test-snap-component-refreshes
+
+execute: |
+  snap refresh --hold
+
+  snap install test-snap-component-refreshes+one+two --revision=3 --edge
+
+  # this snap uses a default track "custom", so we should be tracking
+  # custom/edge
+  snap list test-snap-component-refreshes | awk 'NR != 1 { print $4 }' | MATCH 'custom/edge'
+
+  # verify that the components are installed with the correct revisions (these
+  # are component revisions, not snap revisions)
+  test-snap-component-refreshes one | MATCH '.*revision 3$'
+  test-snap-component-refreshes two | MATCH '.*revision 3$'
+
+  # test refreshing while providing a revision
+  snap refresh test-snap-component-refreshes --revision=4
+  test-snap-component-refreshes one | MATCH '.*revision 4$'
+  test-snap-component-refreshes two | MATCH '.*revision 4$'
+
+  # test just a normal refresh
+  snap refresh test-snap-component-refreshes
+  test-snap-component-refreshes one | MATCH '.*revision 5$'
+  test-snap-component-refreshes two | MATCH '.*revision 5$'
+
+  # candidate has the same snap revision as edge, but it contains a different
+  # set of component revisions
+  snap refresh test-snap-component-refreshes --candidate
+  test-snap-component-refreshes one | MATCH '.*revision 7$'
+  test-snap-component-refreshes two | MATCH '.*revision 6$'
+
+  # go back to a revision we've already installed
+  snap refresh test-snap-component-refreshes --revision=4
+  test-snap-component-refreshes one | MATCH '.*revision 4$'
+  test-snap-component-refreshes two | MATCH '.*revision 4$'
+
+  # snap revision in beta is missing the "two" component, so it shouldn't be
+  # linked
+  snap refresh test-snap-component-refreshes --beta
+  test-snap-component-refreshes one | MATCH '.*revision 6$'
+  not test-snap-component-refreshes two
+
+  # although revision 4 does have the "two" component available, it doesn't get
+  # linked since it is not installed for the current revision
+  snap refresh test-snap-component-refreshes --revision=4
+  test-snap-component-refreshes one | MATCH '.*revision 4$'
+  not test-snap-component-refreshes two
+
+  # since revision 4 of the "two" component is not referenced by anything else
+  # in the sequence, it should be unlinked and discarded
+  snap tasks --last=refresh-snap | MATCH 'Unlink.*test-snap-component-refreshes+two'
+  snap tasks --last=refresh-snap | MATCH 'Discard.*test-snap-component-refreshes+two'
+
+  # note that a revert does bring back the "two" component, since it was
+  # installed when revision 5 was last installed
+  snap revert test-snap-component-refreshes --revision=5
+  test-snap-component-refreshes one | MATCH '.*revision 7$'
+  test-snap-component-refreshes two | MATCH '.*revision 6$'