Engineering Standards & Testing

To maintain production stability across all 35 Edge Functions, engineers must adhere to the following coding conventions and testing practices.

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1. Coding & TypeScript Conventions

Explicit Imports

Always import packages from verified Deno registries or ESM CDNs with pinned version numbers:

// Standard library (pinned release)
import { serve } from "https://deno.land/std@0.168.0/http/server.ts";

// Supabase client (pinned release via esm.sh)
import { createClient } from "https://esm.sh/@supabase/supabase-js@2.39.0";

Standard Handler Pattern

Every Edge Function must implement the standard CORS preflight check and wrapped error handling:

import { serve } from "https://deno.land/std@0.168.0/http/server.ts";

export const corsHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Headers': 'authorization, x-client-info, apikey, content-type',
  'Access-Control-Allow-Methods': 'POST, GET, OPTIONS',
};

serve(async (req: Request) => {
  // 1. Handle preflight OPTIONS
  if (req.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders });
  }

  try {
    // 2. Validate input and authenticate
    const payload = await req.json();

    // 3. Execute domain logic
    const result = await processDomainLogic(payload);

    // 4. Return success response
    return new Response(JSON.stringify({ success: true, data: result }), {
      status: 200,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  } catch (error) {
    console.error(`[FUNCTION_ERROR]:`, error);

    // 5. Return sanitized error
    return new Response(JSON.stringify({
      success: false,
      error: error instanceof Error ? error.message : 'Unknown server error',
    }), {
      status: 400,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  }
});

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2. Formatting & Linting

We enforce Deno’s native formatting and linter tools. Run before opening pull requests:

# Check formatting
deno fmt --check

# Apply formatting
deno fmt

# Run static analysis / linter
deno lint

---

3. Writing Unit Tests

Tests are authored using Deno.test and standard assertions from std/testing/asserts.ts:

Example: Testing Calculation Logic (billing-calculator_test.ts)

import { assertEquals } from "https://deno.land/std@0.168.0/testing/asserts.ts";
import { calculateMemberBalance } from "./calculator_utils.ts";

Deno.test("Calculates net bill with 100% solar coverage correctly", () => {
  const result = calculateMemberBalance({
    consumedKwh: 150,
    generatedShareKwh: 150,
    tariffRatePln: 0.85,
    vatRate: 0.23,
  });

  // Since generation covers consumption, net energy cost is 0 PLN (only fixed fees)
  assertEquals(result.netEnergyCostPln, 0.0);
  assertEquals(result.grossTotalPln > 0, true);
});

Running Tests Locally

deno test --allow-env --allow-net