It's worth pointing out that Citizenship is a legal formality. To apply, someone must already have indefinite leave to remain in the UK, no criminal record, pay income tax and so on. Anyone who is eligible can already work, own property and vote. The issues surrounding Citizenship and its test are therefore different to those about immigration, asylum, refugees and so on. It's about becoming official, a bit like marriage compared with living together.
David Edgar freely admits the style of Testing the Echo is something of a departure from his usual plays. He describes it as fragmented and cinematic - cramming 68 scenes into just under 2 hours. There's no interval which is good as it would break the momentum of the piece - it doesn't have the orchestrated climaxes of a traditional piece. 8 actors portray 33 characters, with everyone playing multiple parts and nationalities. Farzana Dua Elahe probably has the most demanding job, alternating between Jasminka, an Albanian au pair/sex worker and Muna, a 7 or 8 year old Pakistani girl who has grown up in Birmingham. The whole company is utterly credible in all their roles, and both they and the script treat the characters with respect. You may not agree with them but they are more than vessels for a set of beliefs.
The central drama, if there is just one, occurs between Emma, the ESOL teacher and Nasim, a strict muslim from Egypt. Nasim sees Emma as bullying when she insists they discuss things which are haram (forbidden). Emma can't tolerate Nasim's refusal to attend classes given by a homosexual teacher. Both viewpoints are dealt with sympathetically, leaving the audience to decide whether there's a right and wrong. Emma (Teresa Banham) is caught literally between her middle class dinner party and her unbending student. (The dinner party is one of two slices of Britishness we are given. The other is, of course, football!)
And the background to the title? It could be a Citizen-to-be reconciling British culture with echoes of a previous life, or the audience's testing their own beliefs as echoed back at them from the stage. Edgar explains it as coming from one culture echoing another, like a reflection, and also with typical humour, from the famous piece of advice for tourists to be sure and test the famous echo in the Reading Room at the British Library! Like the rest of the play it's open to some interpretation, it needs a little unpacking, but it's well-crafted and well worth it.