CDK and batch build - aws-cdk

Question

I am trying to have cypress tests run in parallel in codepipeline/codebuild as documented here: https://docs.cypress.io/guides/continuous-integration/aws-codebuild#Parallelizing-the-build
I am reading aws docs here:
https://docs.aws.amazon.com/codebuild/latest/userguide/batch-build-buildspec.html#build-spec.batch.build-list
This is what I have got so far:
import * as cdk from '#aws-cdk/core';
import * as codebuild from '#aws-cdk/aws-codebuild';
import * as iam from '#aws-cdk/aws-iam';
import { defaultEnvironment, NODE_JS_VERSION } from './environments/base-environment';
import { projectEnvironmentVars } from './environments/e2e-tests-project-environment';
// import { createReportGroupJsonObject } from '../../utils/utils';
// import { Duration } from '#aws-cdk/core'
interface RunTestsProjectProps {
testsBucketName: string,
testsBucketArn: string,
targetEnv: string,
repoType: string,
role: iam.Role,
codeCovTokenArn: string,
}
export class RunTestsProject extends codebuild.PipelineProject {
constructor(scope: cdk.Construct, id: string, props: RunTestsProjectProps) {
const { testsBucketName, testsBucketArn, targetEnv, repoType, codeCovTokenArn } = props
super(scope, id, {
projectName: id,
role: props.role,
environment: defaultEnvironment,
environmentVariables: projectEnvironmentVars({ testsBucketName, testsBucketArn, targetEnv, repoType, codeCovTokenArn }),
timeout: cdk.Duration.hours(3),
buildSpec: codebuild.BuildSpec.fromObject({
version: '0.2',
phases: {
install: {
'runtime-versions': {
nodejs: NODE_JS_VERSION
}
},
build: {
commands: [
'if [ ! -f "${CODEBUILD_SRC_DIR}/scripts/assume-cross-account-role.env" ]; then echo "assume-cross-account-this.role.env not found in repo" && aws s3 cp s3://${ARTIFACTS_BUCKET_NAME}/admin/cross-account/assume-cross-account-role.env ${CODEBUILD_SRC_DIR}/scripts/; else echo "Overriding assume-cross-account-role.env from repo"; fi',
'. ${CODEBUILD_SRC_DIR}/scripts/assume-cross-account-role.env',
'bash ${CODEBUILD_SRC_DIR}/scripts/final-tests.sh'
],
batch: {
'fail-fast': false,
'build-list': []
}
},
},
artifacts: {
files: '**/*'
},
})
});
}
}
what should I add in the build-list part to have multiple builds running
I tried
'build-list': { identifier: 'build1', identifier: 'build2' }
but this looks like incorrect syntax.
The number of builds should ideally be based on the cypress grouping. Can it be dynamic or has to be defined statically?