improv: include example tests in make tests

[to-mc]

Issue #, if available:

Description of changes:

Update pytest config to run example tests. Update tests in example/tests to specify env vars as fixture without requiring user to pass them at runtime.

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

Ignore if it's not a breaking change

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #63 into develop will increase coverage by 0.60%.
The diff coverage is n/a.

@@ Coverage Diff @@## develop #63 +/- ##
============================================
+ Coverage 99.39% 100.00% +0.60% 
============================================
Files 15 15 Lines 496 496 Branches 45 45 ============================================
+ Hits 493 496 +3 + Misses 3 0 -3 

Impacted Files	Coverage Δ
aws_lambda_powertools/tracing/extensions.py	100.00% <0.00%> (+75.00%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 158fd57...beb8c51. Read the comment docs.

[heitorlessa]

Two quick questions as everything else look great.

1. For those trying to test/deploy the example directly, do we need to update the README given these changes?

2. Could you add the POWERTOOLS_METRICS_NAMESPACE env in SAM back?

I've run through all steps after checking out this PR and am hitting the namespace issue (template.yaml)

---

sam local invoke HelloWorldFunction --event events/event.json

2020-06-0714:19:16,866aws_lambda_powertools.metrics.base [DEBUG] Serializing...
2020-06-0714:19:16,866aws_lambda_powertools.metrics.base [DEBUG] ValidatingserializedmetricsagainstCloudWatchEMFschema
[ERROR] SchemaValidationError: Invalidformat. Error: data._aws.CloudWatchMetrics[0].Namespacemustbestring, Invaliditem: data._aws.CloudWatchMetrics[0].NamespaceTraceback (mostrecentcalllast):
File"/var/task/aws_lambda_powertools/metrics/metrics.py", line110, indecoratemetrics=self.serialize_metric_set()
File"/var/task/aws_lambda_powertools/metrics/base.py", line186, inserialize_metric_setraiseSchemaValidationError(message)

[heitorlessa]

Need to re-add POWERTOOLS_METRICS_NAMESPACE back to SAM template as it fails when it runs locally

[to-mc]

Need to re-add POWERTOOLS_METRICS_NAMESPACE back to SAM template as it fails when it runs locally

I added this env var back in PR #62. I just merged develop into this branch so you should see it now.

[to-mc]

Two quick questions as everything else look great.

1. For those trying to test/deploy the example directly, do we need to update the README given these changes?
2. Could you add the POWERTOOLS_METRICS_NAMESPACE env in SAM back?

I've run through all steps after checking out this PR and am hitting the namespace issue (template.yaml)

sam local invoke HelloWorldFunction --event events/event.json

2020-06-0714:19:16,866aws_lambda_powertools.metrics.base [DEBUG] Serializing...
2020-06-0714:19:16,866aws_lambda_powertools.metrics.base [DEBUG] ValidatingserializedmetricsagainstCloudWatchEMFschema
[ERROR] SchemaValidationError: Invalidformat. Error: data._aws.CloudWatchMetrics[0].Namespacemustbestring, Invaliditem: data._aws.CloudWatchMetrics[0].NamespaceTraceback (mostrecentcalllast):
File"/var/task/aws_lambda_powertools/metrics/metrics.py", line110, indecoratemetrics=self.serialize_metric_set()
File"/var/task/aws_lambda_powertools/metrics/base.py", line186, inserialize_metric_setraiseSchemaValidationError(message)

README is updated already - please let me know if the steps don't work for you.

[heitorlessa]

Just pulled, and it's all working now ;) Merging!