Configure bats and add unit test

test/.shellcheckrc

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+external-sources=true

test/README.md

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+# Use bats in Repositories
+
+Create a repository...
+
+Create a structure with submodules, e.g:
+
+```plain
+src/
+    <project>.bash
+    ...
+test/
+    bats/               <- submodule
+    test_helper/
+        bats-support/   <- submodule
+        bats-assert/    <- submodule
+    <test>.bats
+    ...
+```
+
+```bash
+git submodule add https://github.com/bats-core/bats-core.git test/bats
+```
+
+```bash
+git submodule add https://github.com/bats-core/bats-support.git test/test_helper/bats-support
+```
+
+```bash
+git submodule add https://github.com/bats-core/bats-assert.git test/test_helper/bats-assert
+```
+
+```bash
+git add .
+```
+
+```bash
+git commit -m "Add bats as submodules"
+```
+
+```bash
+git push
+```
+
+Init and update all submodules:
+
+```bash
+git submodule update --init --recursive
+```

test/test-call-with-arguments.bats

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+# Run from project dir:
+# ./test/bats/bin/bats test/test-call-with-arguments.bats
+
+setup() {
+    load 'test_helper/test-setup'
+    init_bats
+
+    chmod +x src/simbashlog.bash
+}
+
+teardown() {
+    chmod -x src/simbashlog.bash
+}
+
+@test "simplest call with arguments" {
+    run simbashlog.bash -a console -s error --message 'An error occured'
+    remove_ansi_codes_from_output
+
+    [[ "$output" == "[ERROR] - An error occured" ]]
+}

test/test_helper/test-setup.bash

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+#!/usr/bin/env bash
+
+function init_bats {
+    load 'test_helper/bats-support/load'
+    load 'test_helper/bats-assert/load'
+
+    # get the containing directory of this file
+    # use $BATS_TEST_FILENAME instead of ${BASH_SOURCE[0]} or $0,
+    # as those will point to the bats executable's location or the preprocessed file respectively
+    PROJECT_ROOT="$(cd "$(dirname "$BATS_TEST_FILENAME")/.." >/dev/null 2>&1 && pwd)"
+    # make executables in src/ visible to PATH
+    PATH="$PROJECT_ROOT/src:$PATH"
+}
+
+function remove_ansi_codes_from_output {
+    echo "Actual output with ansi codes: '$output'"
+    output=$(echo "$output" | sed -r 's/\x1B\[[0-9;]*[mK]//g')
+    echo "Actual output without ansi codes: '$output'"
+}