Address review comments and fix tests to work in the new setup.

src/darwin/Framework/CHIP/MTRDevice.mm

@@ -1627,7 +1627,9 @@ static BOOL AttributeHasChangesOmittedQuality(MTRAttributePath * attributePath)
 
     // Send read request to device if any of the following are true:
     // 1. Subscription not in a state we can expect reports
-    // 2. The attribute has (or is assumed to have) the Changes Omitted quality, so we won't get reports for it.
+    // 2. The attribute has the Changes Omitted quality, so we won't get reports for it.
+    // 3. The attribute is not in the spec, and the read params asks to assume
+    //    an unknown attribute has the Changes Omitted quality.
     if (![self _subscriptionAbleToReport] || hasChangesOmittedQuality) {
         // Read requests container will be a mutable array of items, each being an array containing:
         //   [attribute request path, params]

src/darwin/Framework/CHIPTests/MTRDeviceTests.m

@@ -1518,6 +1518,10 @@ - (void)test017_TestMTRDeviceBasics
     [self waitForExpectations:@[ onTimeWriteSuccess, onTimePreviousValue ] timeout:10];
 
     // Test if errors are properly received
+    // TODO: We might stop reporting these altogether from MTRDevice, and then
+    // this test will need updating.
+    __auto_type * readThroughForUnknownAttributesParams = [[MTRReadParams alloc] init];
+    readThroughForUnknownAttributesParams.assumeUnknownAttributesReportable = NO;
     XCTestExpectation * attributeReportErrorExpectation = [self expectationWithDescription:@"Attribute read error"];
     delegate.onAttributeDataReceived = ^(NSArray<NSDictionary<NSString *, id> *> * data) {
         for (NSDictionary<NSString *, id> * attributeReponseValue in data) {
@@ -1526,8 +1530,9 @@ - (void)test017_TestMTRDeviceBasics
             }
         }
     };
+
     // use the nonexistent attribute and expect read error
-    [device readAttributeWithEndpointID:testEndpointID clusterID:testClusterID attributeID:testAttributeID params:nil];
+    [device readAttributeWithEndpointID:testEndpointID clusterID:testClusterID attributeID:testAttributeID params:readThroughForUnknownAttributesParams];
     [self waitForExpectations:@[ attributeReportErrorExpectation ] timeout:10];
 
     // Resubscription test setup

src/darwin/Framework/CHIPTests/MTRSwiftDeviceTests.swift

@@ -287,6 +287,10 @@ class MTRSwiftDeviceTests : XCTestCase {
         wait(for: [ expectedValueReportedExpectation, expectedValueRemovedExpectation ], timeout: 5, enforceOrder: true)
 
         // Test if errors are properly received
+        // TODO: We might stop reporting these altogether from MTRDevice, and then
+        // this test will need updating.
+        let readThroughForUnknownAttributesParams = MTRReadParams()
+        readThroughForUnknownAttributesParams.shouldAssumeUnknownAttributesReportable = false;
         let attributeReportErrorExpectation = expectation(description: "Attribute read error")
         delegate.onAttributeDataReceived = { (data: [[ String: Any ]]) -> Void in
             for attributeReponseValue in data {
@@ -296,7 +300,7 @@ class MTRSwiftDeviceTests : XCTestCase {
             }
         }
         // use the nonexistent attribute and expect read error
-        device.readAttribute(withEndpointID: testEndpointID, clusterID: testClusterID, attributeID: testAttributeID, params: nil)
+        device.readAttribute(withEndpointID: testEndpointID, clusterID: testClusterID, attributeID: testAttributeID, params: readThroughForUnknownAttributesParams)
         wait(for: [ attributeReportErrorExpectation ], timeout: 10)
 
         // Resubscription test setup