Do not allow empty env vars (#5983)

Fixes #5026 

Signed-off-by: Priyambada Roul <[email protected]>

Author: roulpriya

core/src/main/java/org/testcontainers/utility/TestcontainersConfiguration.java

@@ -230,7 +230,10 @@ private String getConfigurable(
         }
 
         if (environment.containsKey(envVarName)) {
-            return environment.get(envVarName);
+            String value = environment.get(envVarName);
+            if (!value.isEmpty()) {
+                return value;
+            }
         }
 
         for (final Properties properties : propertiesSources) {

core/src/test/java/org/testcontainers/utility/TestcontainersConfigurationTest.java

@@ -126,6 +126,14 @@ public void shouldReadDockerSettingsFromUserProperties() {
             .isEqualTo("some value");
     }
 
+    @Test
+    public void shouldNotReadSettingIfCorrespondingEnvironmentVarIsEmptyString() {
+        environment.put("DOCKER_FOO", "");
+        assertThat(newConfig().getEnvVarOrUserProperty("docker.foo", "default"))
+            .as("reads unprefixed env vars for docker. settings")
+            .isEqualTo("default");
+    }
+
     @Test
     public void shouldNotReadDockerClientStrategyFromClasspathProperties() {
         String currentValue = newConfig().getDockerClientStrategyClassName();