should() chaining (#6128)

packages/driver/src/cy/assertions.js

@@ -284,7 +284,18 @@ const create = function (state, queue, retryFn) {
         // assertions
         if (cmdHasFunctionArg(cmd)) {
           let index = cmd.get('assertionIndex')
-          const assertions = cmd.get('assertions')
+          let assertions = cmd.get('assertions')
+
+          // https://github.com/cypress-io/cypress/issues/4981
+          // `assertions` is undefined because assertions added by
+          // `should` command are not handled yet.
+          // So, don't increase i and go back to the last command.
+          if (!assertions) {
+            i -= 1
+            cmd = cmds[i - 1]
+            index = cmd.get('assertionIndex')
+            assertions = cmd.get('assertions')
+          }
 
           // always increase the assertionIndex
           // so our next assertion matches up

packages/driver/test/cypress/integration/commands/assertions_spec.js

@@ -211,6 +211,29 @@ describe('src/cy/commands/assertions', () => {
         })
       })
 
+      it('can be chained', () => {
+        cy.wrap('ab')
+        .should((subject) => {
+          expect(subject).to.be.a('string')
+          expect(subject).to.contain('a')
+        })
+        .should((subject) => {
+          expect(subject).to.contain('b')
+          expect(subject).to.have.length(2)
+        })
+        .and((subject) => {
+          expect(subject).to.eq('ab')
+          expect(subject).not.to.contain('c')
+        })
+        .then(function () {
+          expect(this.logs.length).to.eq(8)
+
+          this.logs.slice(1).forEach((log) => {
+            expect(log.get('name')).to.eq('assert')
+          })
+        })
+      })
+
       context('remote jQuery instances', () => {
         beforeEach(function () {
           this.remoteWindow = cy.state('window')