Add test coverage

src/test/java/dev/kruhlmann/imgfloat/config/SystemEnvironmentValidatorTest.java

@@ -0,0 +1,57 @@
+package dev.kruhlmann.imgfloat.config;
+
+import static org.assertj.core.api.Assertions.assertThatCode;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.core.env.Environment;
+import org.springframework.mock.env.MockEnvironment;
+import org.springframework.test.util.ReflectionTestUtils;
+
+class SystemEnvironmentValidatorTest {
+
+    @Test
+    void validateSkipsWhenBootstrappedForTests() {
+        Environment environment = new MockEnvironment().withProperty(
+            "org.springframework.boot.test.context.SpringBootTestContextBootstrapper",
+            "true"
+        );
+        SystemEnvironmentValidator validator = new SystemEnvironmentValidator(environment);
+
+        assertThatCode(validator::validate).doesNotThrowAnyException();
+    }
+
+    @Test
+    void validateThrowsWhenRequiredFieldsMissing() {
+        Environment environment = new MockEnvironment();
+        SystemEnvironmentValidator validator = new SystemEnvironmentValidator(environment);
+        setRequiredFields(validator);
+        ReflectionTestUtils.setField(validator, "twitchClientId", "");
+
+        assertThatThrownBy(validator::validate)
+            .isInstanceOf(IllegalStateException.class)
+            .hasMessageContaining("TWITCH_CLIENT_ID");
+    }
+
+    @Test
+    void validateAcceptsAllRequiredFields() {
+        Environment environment = new MockEnvironment();
+        SystemEnvironmentValidator validator = new SystemEnvironmentValidator(environment);
+        setRequiredFields(validator);
+
+        assertThatCode(validator::validate).doesNotThrowAnyException();
+    }
+
+    private void setRequiredFields(SystemEnvironmentValidator validator) {
+        ReflectionTestUtils.setField(validator, "twitchClientId", "client-id");
+        ReflectionTestUtils.setField(validator, "twitchClientSecret", "client-secret");
+        ReflectionTestUtils.setField(validator, "springMaxFileSize", "10MB");
+        ReflectionTestUtils.setField(validator, "springMaxRequestSize", "12MB");
+        ReflectionTestUtils.setField(validator, "assetsPath", "/tmp/assets");
+        ReflectionTestUtils.setField(validator, "previewsPath", "/tmp/previews");
+        ReflectionTestUtils.setField(validator, "dbPath", "/tmp/db");
+        ReflectionTestUtils.setField(validator, "initialSysadmin", "admin");
+        ReflectionTestUtils.setField(validator, "githubOwner", "owner");
+        ReflectionTestUtils.setField(validator, "githubRepo", "repo");
+    }
+}

src/test/java/dev/kruhlmann/imgfloat/util/LogSanitizerTest.java

@@ -0,0 +1,23 @@
+package dev.kruhlmann.imgfloat.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class LogSanitizerTest {
+
+    @Test
+    void sanitizeReturnsNullForNullInput() {
+        assertThat(LogSanitizer.sanitize(null)).isNull();
+    }
+
+    @Test
+    void sanitizeReplacesNewlinesWithUnderscores() {
+        assertThat(LogSanitizer.sanitize("alpha\nBravo\r\ncharlie")).isEqualTo("alpha_Bravo_charlie");
+    }
+
+    @Test
+    void sanitizeLeavesStringsWithoutNewlinesUntouched() {
+        assertThat(LogSanitizer.sanitize("no-newlines-here")).isEqualTo("no-newlines-here");
+    }
+}