Cannot see payload after `mock when`

Let's say i have munit

	<munit:test name="implementation-test-suite-getPPMDetailsTest" doc:id="27323458-a728-425a-9ca7-9dc8df80f360" description="Test">
		<munit:behavior>
			<munit-tools:mock-when doc:name="Mock when" doc:id="69db61d9-d1aa-4490-87df-8b89b6b8f0cc" processor="salesforce:query">
				<munit-tools:with-attributes >
					<munit-tools:with-attribute whereValue="GetCommonContents" attributeName="doc:name" />
				</munit-tools:with-attributes>
				<munit-tools:then-return >
					<munit-tools:payload value="#[MunitTools::getResourceAsString('examples/PPMMock.json')]" mediaType="application/json" />
				</munit-tools:then-return>
				<munit-tools:then-call flow="PPMEntry" />
			</munit-tools:mock-when>
		</munit:behavior>
		<munit:execution >
			<flow-ref doc:name="Flow-ref to getPPMDetails" doc:id="578773fb-3dd0-4d0d-bc2d-b37e4cc97346" name="getPPMDetails"/>
		</munit:execution>
		<munit:validation>
			<munit-tools:assert-that doc:name="Assert that" doc:id="f006b6b4-8342-4c1c-bf8b-c889d606b242" expression="#payload" is="#[MunitTools::notNullValue()]"/>
		</munit:validation>
	</munit:test>

but got empty string '' value when enter to testing flow. What am I doing wrong?